UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALLIDIC: 

1868  2S|£r  19O1 


THE 


PRACTICAL    PHYSICS 


OF  THE 


MODERN    STEAM    BOILER. 


THE 
PRACTICAL  PHYSICS 


OF  THE 


Modern  Steam  Boiler 

BY 

FREDERICK  J.  ROWAN,  A.M.I.C.E.,  M.I.K.S., 

•  i 

Late  Vice- Pres.  Fed.Inst.  M.E., 

Lale  Mem.  Conn.  Soc.  Chem.  Ind., 

Medallist  of  the  Royal  Scottish  Society  of  Arts, 

AUTHOR  OF 


"Fuel  and  its  Applications,"  Vol.  I.  of  Groves  and  Thorp's  Chem.  Technology;  ''Boiler  In- 
crustation and  Corrosion;"  "The  Design  and  Use  of  Boilers;"  "On  Water  Tube  Boilers;'" 
''On  the  Introduction  of  the  Compound  Engine  and  the  Use  of  High  Pressure  Steam;"  "On 
Flame;"  "The  Physical  Conditions  Existing  in  Shale-Distilling  Retorts,"  <frc.,  AT.. 


WITH  A  PREFACE 

BY 

PROF.  R.   H.  THURSTON, 

Cornell  University. 


WITH 


NEW  YORK: 

D.    VAN    NOSTRAND    COMPANY, 

23  MURRAY  AND  27  WARREN  STREETS. 
1903. 


HALUD1E 


CONTENTS. 

PREF\ 

INTRODUCTORY  NOTE  BY  PROFESSOR  R.  H.  THURSTON. 

i-sis  OF  CONTENTS  OF  CHAPTERS. 
CHAITFK        I     INTRODUCTORY— GENERAL  CONSIDERATIONS. 

II.    SUMK  FUNDAMENTAL  ELEMENTS  OF  BOILER  DESIGN. 

III.  COMIU  STION. 

IV.  1  K  \  \  -MISSION  OF  HEAT. 

V.  CIRCULATION  OF  WATER. 

vi.  EFFECTS  OF  TEMPERATURE  ON  TENACITY  AND  DUCTILITY. 

vn.  CORROSION  AND  INCRUSTATION. 

VIII.  HISTORICAL  SKETCH  OF  BOILER  DESIGNS. 

IX.  SOME  TESTS  OF  BOILERS  AND  RESULTS. 

APPENDICES. 
I.    LIST  OF  PAPERS  ON  FORCED  DRAUGHT. 

II.    LIST  OF  PAPERS  ON  HEAT  TRANSMISSION. 
III.    RKPRINT   OF    PAPER    "ON    BOILER    INCRUSTATION    AND 
CORROSION,"  BRITISH  ASSOCIATION,  1876. 


113834 


PREFACE. 


MY  purpose  in  this  book  is  to  give  prominence  to  the  funda- 
mental principles  which  affect  the  form  and  the  action  of  steam 
boilers.  So  many  excellent  treatises  have  been  published  which 
deal  with  the  regulations  concerning,  and  the  structural  details 
of,  boilers  of  the  cylindrical  type  ;  in  a  word,  with  what  may  be 
called  the  Mechanics  of  the  steam  boiler  (i.e.,  treating  of  the 
boiler  as  a  machine),  that  it  has  seemed  to  me  useless  to  repeat 
chapters  on  strength  of  materials,  on  riveting  and  joints,  and  on 
numerous  other  interesting  and  important  matters.  I  have  not 
thought  it  necessary  or  advisable  to  follow  that  well-beaten 
track,  but  have  endeavoured  to  take  another  path,  as  guided  by 
the  indications  of  physical  research  towards  the  goal  of  a  fuller 
understanding  of  the  actions  involved  in  steam  raising,  and  of 
the  requirements  of  efficient  boilers. 

Thus  the  pages  of  this  book  are  occupied  with  the  practical 
Physics  of  the  steam  boiler  (treating  of  the  boiler  as  a  heat 
engine),  and  deal  more  particularly  with  that  which  may  be 
termed  the  modern  form,  the  water-tube  boiler.  My  aim  in  them 
is  therefore  not  so  much  to  treat  of  how  boilers  are  made,  as  to 
consider  on  what  lines  they  may  be  improved. 

One  consequence  of  the  adoption  of  this  aspect  of  the  subject 
is  that  our  point  of  view  is  changed  as  to  several  of  its  depart- 
ments. Thus,  as  to  the  fuel,  instead  of  the  point  being  the 
relation  of  the  quantity  consumed  to  the  area  of  the  grate 


viii.  PREFACE 

surface,  enquiry  is  directed  to  the  question,  what  is  the  largest 
quantity  which  can  be  efficiently  burned  in  given  time  at  the 
highest  temperature  attainable  (with  or  without  a  grate,  in  the 
ordinary  acceptation  of  the  term),  and  with  the  minimum  of 
labour  ? 

With  regard  to  furnace  and  flues,  the  point  of  view  is  changed 
from  the  number  of  inches  of  vacuum  or  plenum  existing  at 
various  points  in  furnace,  flues  or  chimney,  to  the  number  of 
feet  per  second  velocity  at  which  the  hot  gases  traverse  the 
heating  surface.  As  to  the  heating  surface  itself,  instead  of  (as 
formerly)  regarding  the  fixed  ratio  between  heating  surface  and 
grate  area,  we  are  led  to  enquire  what  is  the  proportion  which 
the  number  of  heat  units  transmitted  per  hour,  from  fuel  to 
water,  bears  to  the  area  of  heating  surface  ;  and  as  to  the  water, 
the  question  of  importance  is  not  now,  what  is  the  velocity  of 
flow  produced  by  the  action  of  boiling  in  certain  boilers  (that,  if 
observed  constantly,  may  be  a  good  criterion  of  the  distribution 
of  temperature  in  a  given  boiler)  but  it  is,  what  is  the  greatest 
speed  of  movement  which  we  can  conveniently  impart  to  the 
water,  in  a  direction  contrary  to  that  in  which  the  hot  gases  are 
travelling  ?  Again,  in  former  days,  the  question  of  stresses  was 
regarded  almost  exclusively  from  the  point  of  view  of  the 
external  structure  of  the  boiler  ;  now,  however,  it  is  recognised 
that  many  of  the  most  important  consequences  to  the  safety  or 
life  of  a  boiler  may  result  from  strains  or  stresses  set  up  in  the 
internal  structure  of  the  metal,  whether  accompanied  or  followed 
by  other  physical  or  chemical  action,  and  consequently  our 
point  of  view  here  also  is  altered. 

The  consideration  of  such  questions  necessitates  some 
acquaintance  with  the  physical  principles  which  govern  the 
actions  whose  sphere  is  the  boiler,  and  I  have  consequently 
endeavoured  to  give  some  account  of  investigations  which  throw 
light  in  that  direction. 

Evidence  is  not  wanting  that  we  have  entered  upon  an  era  of 
more  scientific  practice  in  steam  raising  than  used  to  be  the  rule, 


PREFACE.  ix 

and,  that  being  so,  any  measure  of  enlightenment  as  to  the  laws 
which  must  be  obeyed  in  such  practice  is  sure  to  be  useful. 1 

The  fact  that  such  methods  of  treatment  of  an  engineering 
subject  as  the  present  one  are  needed,  or  are  likely  to  be 
welcome,  may  be  taken  as  a  hopeful  sign  that  the  breadth  of  the 
basis  upon  which  engineering  as  a  profession  rests  is  beginning 
to  be  acknowledged. 

To  be  an  Engineer  can  no  longer  be  held  as  equivalent  to 
having  a  mere  possession  of  certain  recognised  methods,  either 
of  calculation  or  of  executing  work.  The  foundation  of  all  good 
practice  must  ultimately  be  an  intelligent  appreciation  of  natural 
phenomena  and  laws,  in  as  far  as  these  have  been  observed  or 
discovered.  And  the  man  who  can  most  fearlessly  and 
thoroughly  make,  in  his  practice,  an  application  of  true  prin- 
ciples, (w^hich  he  may  have  learned  in  connection  with  widely 
different  circumstances)  in  order  to  reach  some  desired  result,  is 
sure  to  be  the  most  efficient  Engineer. 

The  time  was  when  a  book  on  boilers  would  not  have  been 
regarded  even  with  patience,  unless  it  dealt  with  accepted 
practice  and  dwelt  on  its  advantages  ;  or,  at  most,  showed  how 
some  few  details  might  be  improved.  Now,  however,  the  desire 
is  becoming  wide-spread  to  know  in  what  direction  it  is  possible 
generally  to  progress  ;  and  it  does  not  take  long  in  these  days 
for  any  path  to  become  a  beaten  track,  after  it  is  once  marked 
out. 

Fortunately  the  time  has  nearly  gone  by  when  ideas  which 
belong  to  the  physical,  rather  than  to  the  mechanical,  side  of  an 
engineering  problem,  can  be  dismissed  by  means  of  a  cheap 
sneer  at  "  theory,"  for  all  intelligent  educated  men  have  come 
to  understand  that  practice  without  theory  is  a  mere  automaton, 
possessing  no  vital  principle.  In  the  days,  not  yet  ancient,. 

1  While  the  sheets  of  this  volume  are  going  through  the  press  a  paper  by 
Mr.  John  C.  Parker,  "  On  the  Science  of  Steam  Raising,"  has  appeared  in  the 
Proceedings  of  The  Engineers'  Club  of  Philadelphia,  and  I  hail  its  publication 
as  most  valuable  corroborative  testimony  to  the  accuracy  of  these  observations,, 
as  well  as  to  that  of  the  direction  in  which  improvement  must  be  sought. 


x  PREFACE. 

when  "  the  practical  man,"  so-called  (but  who  was,  more 
correctly,  the  man  who  had  learned  a  certain  routine  of  practice, 
beyond  which  he  could  not  see  and  did  not  believe),  was  all- 
important  ;  it  was  enough  for  any  one  to  be  known  as  "  a  man 
with  ideas  "  to  be  at  once  condemned  as  a  visionary.  That 
regime  had  not  the  same  sway  in  other  countries,  such  as 
America,  as  it  held  in  Britain,  but  even  here  there  were  en- 
lightened men  in  the  ranks  of  Engineers  who  never  submitted 
to  it.  Happily  it  is  now  passing  away.  Sir  William  Fairbairn 
thus  writes  (in  his  "  Useful  Information  for  Engineers,"  third 
series,  page  65)  :— 

"  It  is  absurd  to  talk  against  theory,  as  if  a  knowledge  of  the  exact  science 
was  a  dangerous  and  a  useless  attainment  ;  nothing  can  be  more  erroneous 
than  this  impression,  as  on  close  inspection  there  is  no  practice  withouf 
theory,  any  more  than  there  is  any  effect  without  a  cause.  In  the  useful  arts 
theory  can  only  be  considered  dangerous  when  it  is  not  reducible  to  practice, 
and  where  it  tends  to  error  or  false  principles,  which,  in  fact,  is  not  theory 
but  assumption.  The  true  meaning  of  the  term  theory — which  creates  so 
much  alarm  in  the  minds  of  practical  men — is  neither  more  nor  less  than  a 
series  of  definite  rules  by  which  practice  is  governed,  and  through  which  we 
derive,  from  fixed  and  definite  laws,  those  sound  and  unerring  results,  which 
of  all  others  is  the  primary  object  of  practice  to  accomplish.  Let  us,  there- 
fore, abandon  the  '  rule-of-thumb  '  system,  and  cultivate  true  principles  which 
should  never  be  separated  from  the  twin  sisters  of  Science  and  Art." 

Thomas  De  Quincy  gives,  in  his  "  Miscellaneous  Essays  and 
Logic  of  Political  Economy  "  (vol.  xii.,  p.  333),  a  translation  of 
Kant's  essay  "  On  the  common  saying  that  such  or  such  a  thing 
may  be  true  in  theory,  but  does  not  hold  good  in  practice,"  the 
following  extract  from  which  may  well  be  placed  alongside  of 
Sir  Wm.  Fairbairn's  pithy  remarks  : — 

"  It  is  far  more  tolerable  that  an  unlearned  person  should  represent  theory 
as  superfluous  for  the  purposes  of  his  imaginary  practice,  than  that  a  shallow 
refiner,  whilst  conceding  the  value  of  theory  for  speculation  and  scholastic 
uses,  should  couple  with  this  concession  the  doctrine  that  in  practice  the  case 
is  otherwise  ;  and  that,  upon  coming  out  of  the  schools  into  the  world,  a  man 
will  be  made  sensible  of  having  pursued  mere  philosophic  dreams.  In  short, 
that  what  sounds  well  in  theory  is  not  merely  superfluous,  but  absolutely 
false  in  practice.  Now  the  practical  engineer  who  should  express  himself  in 
these  terms  upon  the  science  of  mechanics,  or  the  artillery  officer  who  should 
:say  of  the  doctrine  of  projectiles,  that  the  theory  of  it  was  conceived  indeed 
with  great  subtlety,  but  was  of  little  practical  value,  because  in  the  actual 


PREFACE.  xi 

exercise  of  the  art  it  was  found  that  the  experimental  results  did  not  conform 
to  the  theory,  would  expose  themselves  to  derision.  For  supposing,  that  in  the 
first  case,  should  be  superadded  to  the  theory  of  mechanics  that  of  friction  ; 
and  that  in  the  second,  to  the  theory  of  projectiles  were  superadded  that  of 
the  resistance  of  the  air — which  in  effect  amounts  to  this,  that  if,  instead  of 
rejecting  theory,  still  more  theory  were  added — in  that  case  the  results  of  the 
abstract  doctrine  and  of  the  experimental  practice  would  coincide  in  every 
respect." 

In  the  following  pages  I  have  adhered  to  my  usual  practice  of 
endeavouring  in  every  case  scrupulously  to  acknowledge  the 
source  of  my  information,  either  in  foot  notes  or  in  the  text. 
In  doing  so  I  no  doubt  expose  myself  to  the  criticism  that  a 
portion,  perhaps  even  a  large  portion,  of  my  writing  is  not 
original,  but  I  prefer  that  to  the  meanness  (which  is,  unfortun- 
ately, too  often  met  with)  of  appropriating  the  thoughts  or 
words  of  another  without  acknowledging  their  author,  or  to  the 
vanity  which  makes  use  of  borrowed  plumes  in  the  delusive 
hope  that  the  fraud  will  not  be  detected  by  those  who  are  well 
informed. 

It  is  certain  that  only  a  few  can  possess  the  means  or  the 
opportunity  for  independent  research  (just  as  no  one  man  could 
invent  all  the  different  boilers  described),  and  consequently  that 
the  majority  must  be  content  to  learn  from  them,  using  the  re- 
sults of  investigations  analytically  or  synthetically,  as  illustrations 
or  as  a  basis  for  deduction.  It  is  a  mistake  to  think  that  there 
can  be  no  originality  in  such  a  use  of  these  results.  On  the 
contrary,  in  these  days  invention  and  improvement  must  in  the 
main  proceed  in  the  direction  of  the  adaptation  of  materials  and 
knowledge  already  accumulated. 

The  major  part  of  this  book  was  written  early  in  1898,  but 
its  completion  was  delayed  by  the  necessarily  tedious  ex- 
amination of  patent  office  records  which  was  required  for  the 
preparation  of  Chapter  VIII.  Such  an  examination,  in  addition 
to  affording  historical  data,  furnishes  proof  that  whilst  there 
must  be  progress  in  knowledge  and  skill,  the  attempt  to  intrude 
the  term  "  evolution  "  into  engineering  science  is  an  erroneous 
one.  However  plausible  the  theory  which  is  denominated  by 


xii  PREFACE. 

that  term  may  be,  as  applied  to  organic  structures  considered 
from  a  human  standpoint,  it  can  have  no  proper  application  in 
engineering  as  regards  either  inventions  or  the  inventors  them- 
selves. As  to  the  former,  some  of  the  oldest  inventions  are 
found  to  display  the  most  advanced  ideas,  and,  with  regard  to 
the  latter,  it  has  repeatedly  been  shown  that  nearly  all  great 
improvements  have  been  introduced  from  the  outside  of  the 
special  branch  of  engineering  to  which  they  apply.  Develop- 
ment and  refinement  are  undoubtedly  found,  but  these  apply 
either  to  the  form,  or  to  the  completeness  of  the  detail,  of 
structures  or  machines  of  kinds  the  use  of  which  is  continued 
long  enough,  or  repeated  frequently  enough,  to  permit  of  ex- 
perience being  gained  with  them.  u  Environment  "  in  engin- 
eering resolves  itself  into  a  question  of  that  experience,  com- 
bined with  the  essential  elements  of  the  quality  of  the  materials 
and  the  methods  of  construction,  which  are  available  at  any 
given  time.  These  latter  have  undoubtedly  exercised  the 
principal  influence  on  development,  and  we  find  that  many 
modern  ideas  of  design  are  merely  old  ones  revived  under 
circumstances  in  which  both  the  means  of  carrying  them  out 
successfully  and  the  opportunity  for  their  being  employed 
profitably  have  come  into  existence. 

Since  the  completion  of  the  manuscript  of  this  volume  a 
Committee  to  investigate  the  subject  of  the  water-tube  boilers 
in  the  Royal  Navy  has  been  appointed  by  the  House  of 
Commons  under  the  recommendation  of  the  Rt.  Hon.  G.  J. 
Goschen,  then  First  Lord  of  the  Admiralty  ;  and  after  some 
months  of  enquiry  a  preliminary  Report  has  been  issued.  The 
period  of  experimental  trials  of  different  designs  of  water-tube 
boilers  has  since  then  been  entered  upon,  and  it  is  probable 
that  a  further  Report  will  emanate  from  the  Committee,  although 
not  for  a  considerable  time. 

It  was  to  be  expected  that  a  Committee,  nominated  in  con- 
sequence of  political  pressure,  would  not  in  its  constitution 
prove  entirely  satisfactory  to  the  engineers  and  experts  of  the 


PREFACE.  xiii 

country  ;  yet,  although  the  chief  qualification  for  appointment 
to  this  Committee  seems  to  have  been  engineering  skill  combined 
with  an  absence  of  special  experience  of  water-tube  boilers, 
there  are  few  who  can  object  to  the  main  direction  which  the 
recommendations  of  the  Committee  have  so  far  taken. 

Whether  a  satisfactory  solution  of  the  water-tube  boiler 
question  can  be  reached  during  the  lifetime  of  this  Committee 
remains  to  be  seen. 

In  this  connection  the  remarks  in  a  paper  by  Mr.  John  C. 
Parker,  of  Philadelphia,  "  On  the  Science  of  Steam-making " 
(published  while  this  book  is  passing  through  the  press), 
deserve  some  attention. 

My  best  acknowledgments  are  due  to  Professor  R.  H. 
Thurston,  of  Sibley  College,  Cornell  University,  Ithaca,  N.Y., 
U.S.A.,  not  only  for  much  information  derived  from  his  various 
technical  works,  but  also  for  the  kindness  with  which  he 
consented  to  write  an  introductory  note  to  this  volume. 

I  am  also  indebted  to  many  manufacturers  of  boilers  for 
information  about  their  special  generators,  and  for  the  loan  of 
woodcuts  required  for  illustrations  ;  and  to  some  personal 
friends  for  valuable  assistance  and  advice  in  the  work  of  pre- 
paring this  book.  Amongst  the  former  are  the  Councils  of 
the  Institution  of  Civil  Engineers  and  the  Institution  of 
Engineers  and  Shipbuilders  in  Scotland  ;  Messrs.  Willans  and 
Robinson,  Ltd.,  Henry  Watson  &  Sons,  Simpson  &  Bodman, 
The  Actiebolaget  de  Lavals  Angturbin,  Robertson  &  Outram, 
Clarke,  Chapman  &  Co.,  Ltd.,  Haythorn  &  Stuart,  B.  R. 
Rowland  &  Co.,  Ltd.,  R.  Hornsby  &  Sons,  Ltd.,  Prof.  W.  H. 
Watkinson,  Mr.  J.  W.  Reed  and  Mr.  R.  Dunell  ;  whilst  amongst 
the  latter  are  Prof.  E.  J.  Mills,  D.Sc.,  F.R.S.,  Mr.  J.  T.  Milton  and 
Mr.  E.  H.  Parker. 

I  wish  also  to  acknowledge  the  assistance  rendered  by  my 
son,  Mr.  Stephen  Rowan,  in  the  preparation  of  drawings  for 
some  of  the  illustrations. 


INTRODUCTORY    NOTE. 


BY  ROBERT  H.  THURSTON,  LL.D.,  DR.ENG'G.;  PAST- PRESIDENT 

AMERICAN  SOCIETY  MECHANICAL  ENGINEERS,  &c. ; 
DIRECTOR  OF  SIBLEY  COLLEGE,  CORNELL  UNIVERSITY. 


IN  the  selection  of  his  title,  "  The  Practical  Physics  of  the 
Modern  Steam-Boiler,"  the  author  has  admirably  denned  his 
field  of  exposition.  It  is  a  field,  also,  which  offers  a  large 
opportunity,  and  Mr.  Rowan  has  well  availed  himself  of  it, 
greatly  to  the  advantage  of  the  reader,  professional  as  well  as 
novice.  He  has  so  treated  his  subject  as  to  lay  large  stress  upon 
the  distinguishing  adjective  in  his  title,  "practical"  collecting 
information  from  the  world's  literature  of  engineering  bearing 
upon  the  practical  development  of  the  art  of  steam-boiler 
construction  and  on  the  practical  applications  of  scientific 
principles.  The  book  is  not  a  systematic  treatise  covering  the 
whole  field  of  design,  construction,  and  operation  of  every  class 
of  boiler  ;  nor  is  it  intended  as  such.  It  is  a  discussion  of  a 
defined  and  limited  part  of  that  great  department  of  engineering, 
and  its  illustrations  of  fact  and  principle  are  very  largely  devoted 
to  the  modern  types  of  "  water-tube  "  boilers,  while  the  purpose 
of  its  writer  is  declared  to  be  quite  as  much  the  indication  of  the 
trend  of  improvement  as  the  exhibition  of  their  present  status  as 
apparatus  for  the  evolution  and  storage  of  thermal  energy. 

The  point  of  view  of  the  author  of  this  novel  and  valuable 
contribution  to  the  literature  of  the  subject  is  well  expressed, 
and  the  purpose  held  before  himself '  during  its  preparation  is 
clearly  defined,  by  the  form  given  by  him  to  the  topics  discussed. 
He  would  not  seek  to  learn  the  ratio  of  fuel-consumption  to  the 


xvi.  INTRODUCTORY    NOTE. 

grate-area,  but  rather  the  philosophical  datum  of  real  importance, 
the  ratio  of  area  of  heating  surface  to  fuel  consumed.  He  would 
ascertain  the  conditions  of  maximum  efficiency  both  of  heat 
development  and  of  heat  transfer.  He  studies  the  effect  of 
varying  rates  of  flow  of  furnace  gases  along  the  heating  surfaces 
with  which  they  are  in  contact,  with  the  purpose  of  ascertaining 
the  laws  of  heat-exchange  as  affecting  the  efficiency  of  the 
boiler  as  a  whole.  He  investigates  the  effects  of  chemical  and 
structural  changes,  as  well  as  of  mechanically  applied  stresses, 
upon  the  safety  and  the  endurance  of  the  boiler.  In  the  whole 
work,  it  is  recognized  that  such  a  real  and  practical  and 
applicable  knowledge  of  this,  as  of  any,  department  of  engineering 
must  be  based  upon  scientific  fact,  principle,  and  method  ; 
discovering  by  experience  and  direct  experiment  the  fundamental 
facts,  deducing  by  sound  logic  the  principles  of  which  the  facts 
are  the  illustrations  ;  then  applying  that  knowledge  of  fact  and 
those  accurately  defined  principles  to  the  solution  of  the  equally 
well-defined  problems  of  the  engineer. 

The  modern  and  professional,  as  distinguished  from  the  older 
and  unscientific,  methods  of  engineering  are  thus  illustrated. 
The  engineer  of  the  twentieth  century  designs  rather  than 
invents,  and  secures  a  certainty  of  success  by  systematic  and 
scientific  method,  first  seeking  an  exact  definition  of  his  problem, 
then  proceeding  to  its  solution  by  application  of  deduction  or 
computation  to  each  element  of  the  case  in  a  perfectly  well- 
settled  order  of  sequence.  Engineering  is  to-day  a  more  exact 
science  than  is  any  other  among  the  professions  or  the  vocations 
of  our  modern  world.  Its  practice  involves  larger  and  more 
exact  knowledge  of  nature's  laws  and  of  facts  related  directly  to 
its  tasks  ;  its  schools,  where  most  developed  and  best  adapted 
to  their  purposes,  demand  more  of  the  immatriculates,  and  more 
and  harder  work  for  their  diplomas  and  certificates,  than  do  the 
schools  of  the  so-called  "learned"  professions.  Engineering 
has  already  conquered  its  place  beside  those  especially  honoured 
guilds,  and,  such  are  the  requirements  of  the  modern  industrial 
world,  it  must  soon  make  itself  the  most  learned  of  the  profes- 
sions, in  the  departments  of  applied  science,  if  not  otherwise. 

The  best  engineering  is  that  which  avails  itself  most  intelli- 
gently and  most  universally  and  invariably,  in  every  task,  of 
exactly  known  facts  and  precisely  formulated  principle.  It 


INTRODUCTORY   NOTE,  xvii 

employs  exact  knowledge  rather  than  lt  rule-o'-thumb."  Where 
exact  knowledge  is  not  attainable,  however,  it  does  not  hesitate 
to  use  a  "  nile-o'-thumb "  system,  however  crude,  if  it  seems 
reliable  and  has  been  found  by  experience  to  be  safe  and 
economically  satisfactory.  Like  any  well-trained  physician,  the 
engineer  employs  the  best  means  at  hand  for  the  accomplish- 
ment of  his  purpose,  and  without  stopping  to  inquire  into  its 
authorship. 

In  the  treatise  here  presented  to  the  engineer  interested  in 
steam  production,  I  am  much  interested  in  rinding  so  large  a 
portion  of  the  work  devoted  to  the  water-tube  boiler.  In  a 
report  to  the  American  Institute  of  the  State  of  New  York,  in 
1871,  as  chairman  of  a  committee  which,  for  probably  the  first 
time  in  history,  determined  the  quality  of  steam  supplied  from 
water-tube  and  other  boilers  by  condensation  of  their  whole 
output  during  the  trials,  I  wrote  into  the  summary  of  conclusions 
this  deduction,  that  we  might  even  then  ''look  forward  to  the 
time  when  their  use  will  become  general,  to  the  exclusion  of  the 
older  and  more  dangerous  forms  of  boiler."  * 

Two  fundamental  principles  have  been  enunciated  by  those 
famous  engineers,  John  Stevens  and  William  Fairbairn,  which 
are  more  nearly  complied  with  by  the  water-tube  type  of  boiler 
than  by  the  shell-boiler  : — A  boiler  should  be  so  constructed 
that  it  shall  not  be  liable  to  explosion  ;  the  boiler  should  also  be 
so  constructed  that  should  it  happen,  through  neglect  and  care- 
lessness, inevitably  here  and  there  met  with  in  the  weak 
humanity  which  must  be  entrusted  with  it,  that  explosion  does 
occur,  the  explosion  shall  not  be  dangerous.  The  consideration 
of  these  principles  will  be  found  to  justify  extended  study  of 
promising  types.  The  remark  of  the  author  of  this  treatise  that 
"  there  are  solid  grounds  for  the  opinion  that  further  improve- 
ment is  possible "  affords  additional  reason,  if  other  reason 
seems  needed. 

The  enormous  aggregate  of  information,  from  authoritative 
sources,  here  collected  is  accompanied  by  much  instructive 
comment  and  many  helpful  suggestions,  and  the  book  will  be 

*  Transactions  American  Institute  of  the  State  of  New  York,  1871  ;  Report 
of  Committee  appointed  to  test  Steam-Boilers,  Albany  ;  Argus  Press,  1872. 
See,  also,  this  volume,  page  517. 


xviii  INTRODUCTORY   NOTE. 

found  a  mine  of  valuable  and  solid  learning  in  this  Held.  The 
facts  gathered  together,  and  the  principles  illustrated  and 
elaborated,  the  numerous  drawings  of  the  most  important  inven- 
tions and  constructions,  and  the  systematic  presentation  of  all, 
should  prove  useful  to  every  class  of  readers. 

The  fundamental  problem  of  the  engineer  in  this  department 
of  his  work,  as  in  all  other  fields,  is  a  financial  one.  Given  a 
specific  demand  for  steam  ;  to  provide  that  quantity,  certainly 
and  safely  and  continuously,  at  a  minimum  total  cost,  including 
purchase  and  installation  and  capitalized  current  expenditure, 
for  the  life  of  the  apparatus,  together  with  all  incidentals, 
whether  gains  or  losses,  however  affected  by  the  installation 
of  the  boiler.  This  means  reduction  of  weight,  of  space 
occupied,  of  fuel  consumption  and  labour  costs,  of  preparation  of 
foundations  on  shore  and  displacement  of  valuable  cargo  and 
passenger  accommodation  on  shipboard,  of  transportation  of  sup- 
plies, and  of  removal  of  ash.  This  principle  is  most  completely 
complied  with  when  the  installation  contributes  in  a  maximum 
possible  degree  to  the  dividend-earning  capacity  of  the  enter- 
prise, of  which  it  is  a  material  element,  and  when  the  books  of 
the  treasurer  show  most  satisfactory  balances  so  far  as  affected 
by  its  use.  The  so-called  boiler  efficiency  is  an  essential  factor 
in  this  result,  but  it  is  by  no  means  the  only  one.  The  engineer 
is  thus  necessarily,  if  successful,  a  financier  of  high  rank,  and  his 
success  must  always  be  ultimately  gauged  by  a  monetary 
standard.  There  is  always  a  certain  proportion  and  size  of 
boiler  of  any  one  class  and  type  which  affords  a  solution  of  this 
t(  problem  of  the  golden  mean."  :  In  the  attempted  solution  of 
this  ultimate  problem,  the  knowledge  which  may  be  acquired  in 
the  study  of  ascertained  facts  and  of  established  principles,  such 
as  are  here  brought  together,  the  engineer  will  find  essential  aid. 

*  "  Manual  of  Steam  Boilers."     Thurston.     Chapter  XIII. 


SYNOPSIS    OF    CONTENTS    OF 
CHAPTERS. 


PAGE 

CHAPTER  I.— -INTRODUCTORY         1-9 

The  Water-tube  Boiler  an  Early  Design — Hindrances  to  Recep- 
tion of  New  Ideas — Facility  of  Construction  for  a  time  more  potent 
than  Scientific  Principles  —  Two  Schools  Existent  amongst 
Engineers  from  the  first  —  One  Developed  the  Steam  Engine  on 
the  lines  of  a  Vacuum  Engine  ;,  the  other  as  a  Pressure  Engine — 
Development  of  the  Steam  Engine  as  a  Heat  Engine  found  to 
Proceed  on  Latter  Lines — Increased  Pressures  have  finally  forced 
Water-tube  Boilers  to  the  Front — Difficulties  in  the  Way  Hitherto 
— Present  Aspect  of  the  Subject— Pendred's  Remarks  in  1867  ;  Sir 
F.  Bramwell's  in  1872  ;  Author's  in  1878  ;  Dr.  A.  C.  Kirk's  in 
1887  ;  and  Mr.  M.  Paul's  in  1897  ;  all  Evidence  of  Advancement 
and  the  Need  of  it — Requirements  of  Special  Work  have  called 
out  Special  Designs — In  Future  Design  must  be  Governed  by  the 
Dictates  of  Physical  Science— Insufficiency  of  the  Standard 
Requirements  of  Boiler  Design  as  given  in  Text  Books  referred  to, 
and  their  Defective  Character  as  to  Information  pointed  out — Some 
Points  Demanded  in  a  Good  Boiler 

CHAPTER     II.  —  SOME     FUNDAMENTAL     ELEMENTS     OF     BOILER 

DESIGN 10-49 

Fundamental  Elements  Necessarily  Permanent  —  Laws  of  Fluid 
Pressure  and  those  Governing  Formation  and  Dynamical  Effects 
•of  Steam  must  be  provided  for— Pascal's  Law  of  Fluid  Pressure — 
Effects  as  regards  Form  and  Dimensions — Small  Diameters  and 
Thicknesses  Result  —  The  Unequal  Strains  put  upon  large 
Cylindrical  Forms  —  Deformation  ;  Changes  of  Form  Due  to 
Pressure — Milton's  Measurements — Oscillatory  Strains  and  the 
"Fatigue"  of  Metals — M.  Wohler's  Researches  and  Laws — Causes 
of  Oscillatory  Strains  in  Boilers:  Alterations  of  Steam  Pressure  due 
to  Firing  and  to  Engine  Working  ;  Expansion  and  Contraction  due 
to  Alternations  of  Temperature— Effects  of  Temperature  Strains 
on  Boilers— Rule  for  their  Measurement — Investigations  into 
them  by  Mr.  Yarrow — Dr,  Kirk's  Experiments  on  the  Effects  of 
Overheating  on  Tube  Plates  -Sir  J.  Durston's  Investigations  of  the 
Effects  of  Heat  on  Boilers— Water-tube  Boilers  from  their  Design 
Exempt  from  many  Strains  frit  in  Cylindrical  and  Locomotive 


xx  SYNOPSIS   OF   CONTENTS. 

I'AGE 

Types — Defective  Water-tube  Designs  Exposed  to  Oscillatory  and 
other  Strains — Mr.  Gretchin's  Observations  on  Boilers  of  the 
"  Kherson "  give  Proof  of  the  Existence  of  such  Action- 
Belleville  Design  Specially  Liable  to  Differences  of  Temperatures 
in  Tubes  -  Requirements  of  Boiler  Design  Resulting  from  the 
information  gained. 

CHAPTER  III.— COMBUSTION          50-108 

Problem  of  Steam  Generation  a  Two-fold  One — Combustion 
deals  with  the  first  part,  How  to  obtain  Maximum  of  Heat  from 
the  Fuel— What  is  the  Calorific  Value  of  Fuel— Usually  calculated 
from  Analysis  of  ultimate  Composition — Proximate  Composition  ot" 
Fuels  very  different-  -Complex  Composition  of  Coal — Variation  in 
the  Calorific  Power  of  different  forms  of  Carbon,  and  in  that  of 
different  Hydro-carbons — Physical  State  of  Fuel  before  Combustion 
as  w^ell  as  Chemical  Constitution  affect  its  Heat  of  Combustion- 
Methods  of  Calculating  Calorific  Power  from  Analysis — Results 
yielded  by  Calorimeter  methods — Theoretical  Temperatures  of  Com- 
bustion— Effects  of  Admixture  of  Air-  Fluctuations  of  Temperature 
in  Boiler  Furnaces — Quantity  of  Air,  Theoretical  and  Practical, 
Admitted — Volume  of  Gases  Produced  by  Combustion — Velocity  of 
the  Gases — Effects  of  Pre-heating  the  Air  for  Combustion — 
Temperature  of  the  Exit  Gases — Loss  of  Heat  thereby — Means  for 
Saving  this  Heat — Forced  or  Accelerated  Draught— Defects  of 
Ordinary  Systems  of  Forced  Combustion — External  Combustion 
Chambers — Economy  in  Power  with  Forced  Draught — Increased 
Rapidity  and  Intensity  of  Combustion — Closed  Stokehold  System— 
Howden's  System — Closed  Ashpit  System — Suction  System — 
Varying  Rates  of  Combustion  per  square  foot  of  Grate  Area  with 
different  Air  Pressures — Results  with  Locomotives — Restrictions  as 
to  Air  Pressure — Mr.  Kemp's  Feed  Heaters  for  Waste  Gases- 
Comparisons  with  Mr.  Howden's  Air  Heater — Heat  Absorbing 
Powers  of  Water  and  Air — Improvement  in  Methods  of  Combus- 
tion— Mechanical  Stoker,s — Gas  Firing — £oal  Dust  Firing — Use  of 
External  Firing  Chambers — Combustion  under  Increased  Pressure 
— Calculation  of  its  Effects — Theoretical  Limits — Temperature 
Produced  in  Furnaces  depends  upon  Weight  of  Fuel  Burned  in 
given  Time  and  Space,  and  upon  Pressure — Weight  of  Air  used  per 
pound  of  Fuel  not  a  good  Index — The  Main  Unit  of  Comparison 
for  Boiler  Proportions  should  be  the  Fuel— American  Progress 
in  Methods  of  Combustion  since  this  Chapter  was  written. 

CHAPTER  IV. — TRANSMISSION  OF  HEAT 109-217 

Successful  Transmission  of  Heat  the  Solution  of  Greatest  Problem 
of  Boiler  Design — A  Boiler  Properly  Regarded  as  a  Heat  Engine- 
The  Heat  Efficiency  of  Boilers  as  at  Present  Estimated — Value  of 
Heating  Surface  omitted  in  such  Estimates — A  Standard  of  Heat 
Efficiency  including  Surface  Wanted — Carnot's  Law  as  to  Heat 
Engines — Anderson's  Illustration  of  the  Law-  Methods  of  Increas- 
ing the  Range  of  Temperatures — Transmission  of  Heat  Propor- 
tional to  Difference  of  Temperatures  Clerk  Maxwell's  Formula  for 
Rate  of  Transmission  Peclet's  Experiments- Wiedemann  and 
Franz's  Results  D.  K.  Clark's  Calculations  from  Peclet's  Results- 
Motion  Essential  to  Transmission — Direction  of  currents — Professor 
O.  Reynolds  on  Heat  Transmission — Experiments  with  Steam — 
Hagemann's  Experiments-  -Xichol's  Experiments  Professor  Ser's 


SYNOPSIS   OF   CONTENTS.  xxi 

Results — C.  R.  Land's  Experiments  with  Evaporators — Experiments 
with  Fire  Gases  Graham's  Experiments — Northern  Railway  of 
France  Experiments  with  Locomotive  Boiler-  Hirsch's  Experiments 
on  Evaporation  ;  on  Heat  Transmission  ;  on  Effects  of  Increased 
Viscosity  of  Water  ;  on  Effects  of  Incrustation  ;  on  Effects  of  Flaws 
and  Joints  ;  on  Effect  of  Contact  with  Hot  Brickwork  ;  on  Effects 
of  Oil  and  Grease  Limiting  Circumstances  Affect  Value  of  Experi- 
ments —-Blechy nclen's  Experiments — Reichsanstalt  Experiments— 
Bryant's  Experiments  and  Investigation — Zittenberg's  Experiments 
—Sir  J.  Durston's  Examination  of  Movement  of  Hot  Gases-Spiral 
Vortex  Movement  of  Hot  Gases — Layers  of  Gases — Comparison  of 
Heat  with  Electricity  and  Magnetism— Professor  Perry's  Formula — 
Professor  R.  H.  Smith's  Calculations — Mr.  Hudson's  Calculations  and 
Formula — Importance  of  Velocity  of  Gases — Mr.  Milton's  Estimates 
of  Speed  of  Gases — Prof  Rankine's  Formulae  of  Heat  Transmission 
Professor  Wit/'s  Experiments— Conclusions  from  these  Results. 

CHAPTER  V.     CIRCULATION  OF  WATER 218-270 

Chief  Importance  of  Circulation  connected  with  Heat  Trans- 
mission— Necessity  for  Movement  of  Water — Circulation  of  Water 
usually  Considered  in  View  of  Preservation  of  Boiler  Surfaces — 
Two  Kinds  of  Circulation — Natural  Circulation  Produced  by  Boiling 
-Clerk  Maxwell  on  Boiling  and  on  Convection  Currents — Matthey's 
Experiments  on  Action  of  Bubbles — Halliday  on  Cause  of  Move- 
ment of  Water — Watkinson  on  Effect  of  Bubbles — Action  of  Rapid 
Formation  of  Steam — Effect  in  the  Belleville  Boiler  Model — Down- 
comers — Mr.  C.  Ward  on  Downcomers — Mr.  Yarrow's  Experiments 
on  Downcomers — Chasseloup-Laubat's  Summary — Bellens'  Experi- 
ments— Dubiau's  "  Emulseur  "  Tubes — Thornycroft's  Experiments — 
M.  Normand's  Objections  to  Thornycroft's  Conclusions — Other 
Objections  by  the  Author  and  by  Mr.  Milton — Mr.  Blechy nden's 
Later  Experiments — Apparatus  for  Measuring  Circulation  :  Thorny- 
croft's, Thielmann's,  Watkmson's — Defects  in  the  Latter — Theory 
of  the  Pie/.ometer — Torricelli's  Theorem — Bernoulli's  Theorem — 
Rowan's  Velocity  Gauge  —  Chasseloup-Laubat's  Calculations  — 
Remarks  on  these  Calculations — Forced  or  Mechanical  Circulation 
— Analogy  Derived  from  Heating  Apparatus — Artificial  Circulation 
Produced  by  Automatic  Feeding  Apparatus  or  Emulseurs  not  the 
same  as  Accelerated  Circulation — Benson's  Perhaps  the  First 
Example — Use  of  "  Film  "  Evaporating  system — Critical  Velocity 
Priming — Delayed  Ebullition — Heating  teed  Water— Conditions 
to  be  Realised  in  Order  to  obtain  the  best  Results  with  Boilers. 

CHAPTER    VI.— THE    INFLUENCE   OF    TEMPERATURE   ox  TENACITY 

AND  DUCTILITY     271-320 

Limits  to  the  Heating  of  Boilers  and  Pressures  of  Steam  fixed  by 
Effects  of  High  Temperature  on  Iron  and  Steel — Fairbairn's  Inves- 
tigations— Wertheim's  Experiments — Kupffer's  Experiments — Per- 
manent Dilatation  of  Iron — Fairbairn's  Figures  of  Tensile  Strength  at 
Different  Temperatures— Professor  Kntit  Styffe's  Elaborate  Research 
—On  Fracture  at  High  and  Low  Temperatures — On  Effects  Pro- 
duced on  Specific  Gravity  by  Traction  at  High  Temperatures— Effect 
on  Modulus  of  Elasticity-  Influence  of  Different  Temperatures  on 
Flexion — W.  Parker's  Experiments  Dr.  Kollmann's  Experiments - 
Pisati's  Experiments  with  Wire  -Effect  of  High  Temperature  on  Steel 
•-  Effect  of  Low  Temperature  on  Steel  Effects  of  a  Blue  Heat  on 


xxii  SYNOPSIS   OF   CONTENTS. 

PAGE 

Steel — Professor  Marten's  Report  of  German  Experiments — Special 
Precautions  taken  to  make  the  Tests  a  Complete  Series — Results 
Given  Represented  by  Curves — Diagrams  Permit  of  Comparisons 
between  Leading  Results  for  Different  Qualities  of  Metal  Tested — 
Rudeloff's  Results  for  Manganese  Bronze-Professor  Carpenter's  Tests 
-Diagram  of  Results  at  both  High  and  Low  Temperatures — Investiga- 
tions of  the  Effect  of  High  Temperature  on  the  Strength  of  Copper 
and  various  Alloys — Results  of  Tests — Le  Chatelier's  Experiments 
with  Copper  Wire — Mr.  Stanger's  Experiments  on  Phosphor 
Bronze  and  Alloys — Table  of  Results — Zinc-copper  Alloys  Compared 
with  Tm-copper  Alloys — Effect  of  Addition  of  Aluminium — Results 
of  Various  Experiments  :  German,  American,  English,  and  Swedish, 
Grouped  as  Curves  on  Diagram  by  Professor  Thurston — Some  Con- 
siderations by  M.  Cornut,  tending  to  Modify  Conclusions. 

CHAPTER  VII. — CORROSION  AND  INCRUSTATION  IN  BOILERS...         321-354 

Preservation  of  Boilers  a  Question  of  Cleanliness — First  Ex- 
perience of  Boiler  Corrosion  after  Introduction  of  Compound  Engines 
Presented  Difficulty — No  Previous  Acquaintance  with  the  Action 
amongst  Marine  Engineers — No  General  Knowledge  of  Subject 
— Sea  Water  Scale  Prevented  Corrosion,  but  Caused  Loss  of  Heat — 
Notice  of  Mallet's  Early  Papers  on  the  Subject — His  Work  Directed 
to  the  Question  of  Ships — Papers  of  Humphreys  and  Jack  on  the 
Difficulty  with  Boilers — Conclusion  at  First  Reached  about  Corrosion 
Wrong-Some  Early  Explanations  of  the  Action — Professor  Calvert's 
Work,  Instrumental  in  First  Directing  Engineers-The  Author's  Paper 
of  1876— The  Third  Report  of  Admiralty  Boiler  Committee  in  1877 — 
Subsequent  Papers  on  the  Subiect — Relative  Corrosion  of  Iron  and 
Steel — Mr.  Turner's  Summary — Evidence  of  Bias  in  Later  Writings 
on  Corrosion — Galvanic  Action  and  its  Effects — Mr.  Andrew's  Ex- 
periments— Influence  of  Stress  on  Corrosion — Influence  of  Mill-Scale 
— Electrical  Activity  of  Oxides — Professor  Lewes'  Experiments — 
Mr.  W.  John's  Observations  on  Corrosion  of  a  Steel  Ship — Summary 
of  Chemical  Actions  Involved  in  Corrosion— Absorption  of  Gases 
by  Liquids — Coefficients  of  Absorption — Limits  of  Pressure  used — 
Effects  of  Mixture  of  Gases — Action  of  Water  Vapour — Conditions  of 
Escape  of  Gases  from  Water— Rate  of  Absorption  not  yet  Determined 
by  Experiment — Analogous  Experiment  with  Water  Freed  from 
Air — Effects  of  Increase  of  Temperature  and  Pressure  on  Corrosion 
— Influence  of  Points — Non-uniformity  of  Texture  of  Metals — 
Effect  of  Thinness — Influence  of  Oily  matters — Action  of  Animal 
and  Vegetable  Oils  and  of  Hydrocarbons— Remedy  for  Corrosion 
due  to  Oil — Action  of  Magnesic  Chloride — Need  for  Filters  and 
Evaporators — Use  of  Zinc — Protecting  Surfaces  by  Forming  Incor- 
rodable  Coatings — Professor  Barff's  Plan — The  Author's  Plan — 
Rendering  the  Water  Non-Exciting — Practical  Points  to  be  Observed 
in  Dealing  with  Boilers. 

CHAPTER  VIII. — HISTORICAL  SKETCH  OF  BOILER  DESIGNS  ...         355-509 

Some  Ancient  Forms  referred  to — The  Earliest  Practicable 
Boilers — Various  Methods  employed  for  Raising  Steam — Tank 
Boilers— Flash  Boiler  Plan— Stirring  the  Water— Sub-dividing 
Heating  Surface — Revolving  Boilers — Using  Heated  Oil  to  Transmit 
Heat  to  the  Water — History  of  the  Introduction  of  Sectional  or 
Water-tube  Boilers — Hero's  Designs  not  Boilers — Blakey's  Boiler 
— Fitch  and  Voight's  Boiler — Rumsey's  Boilers — Barlow's  Boiler — 


SYNOPSIS   OF   CONTENTS.  xxiii 

PAGE 

Teschemacher's  Boiler  A  Suggestion  of  a  "Film"  System — 
Payne's  Boiler  and  Flash  Boilers— Jacob  Perkins'  System— Woolf's 
Boiler  —  Cast  Iron  Boilers  —  Stevens'  Boiler  —  Miller's  Boiler- 
Harrison's  Boiler— The  Allen  Boiler — The  Exeter  Boiler.  Hori- 
zontal Tube  Boilers — Different  Groups  of  These.  "  Series  "  and 
"  Parallel  "  Coupling — Action  in  Hori/ontal  Generating  Tubes — 
Hancock's  Early  Boiler— Griffith's  Boiler— Andrew  Smith's  Boiler — 
Alban's  Boiler — The  Belleville  Boilers — Stephen  Wilcox's  Boiler — 
Benson's  Boiler — Williamson  and  Perkins'  Boiler — Boilers  of 
the  ss.  "Montana"  and  "Dakota" — Ramsden's  Boiler — Babcock 
and  Wilcox  Boilers — The  Root  Boiler — Howard's  "Barrow" 
Boiler — Watt's  Boiler — Suckling's  Boiler — Hardingham's  Boiler — 
Lane's  Boiler — Steinmiiller's  Boiler — The  Buttner  Boiler — The 
Xiclausse  Boiler— The  Phleger  Boiler— The  Heine  Boiler— The 
Poole  Boiler— Seaton's  Boiler— The  Lagrafel  D'Allest  Boiler— The 
Oriolle  Boiler— The  Kelly  Boiler— The  Diirr  Boiler— Hornsby's 
Boiler — The  Towne  Boiler — Rainey's  Boiler.  Other  Modifications 
of  the  Horizontal  Tube  Boiler — Boilers  composed  ot\  Horizontal 
Cylinders,  arranged  in  Tiers  or  Concentrically.  Vertical  and  . 
Vertically-Inclined  Water-tube  Boilers — Action  of  Steam  in  Boiling 
must  have  suggested  them  early — History  of  these  Designs, 
supposed  to  begin  with  Trevithick — Distinct  Design  introduced  by 
Jacob  Perkins,  and  followed  by  R.  Prosser,  P.  F.  Joly,  and  E.  Field 
— Notable  Boilers  with  the  Perkins'  Hanging  Tube,  those  of  Field, 
Allen,  Wiegand,  J.  Thorn,  and  Phillips — Boilers  of  Clark,  Steenstrup, 
Eve,  Church,  Summers  and  Ogle,  Trevithick,  Maceroni  and  Squire, 
James,  Craddock,  Clarke  and  Motley,  Johnson,  Rowan  and  Horton, 
Green,  Williamson,  Field,  Twibill,  Jordan,  Howard,  Wiegand, 
Firminich,  Fryer,  Rowan,  Thornycroft,  White,  Yarrow,  Du  Temple, 
Cowles,  Andrews,  Fleming  and  Ferguson,  Normand,  Blechynden, 
Reed,  Maxim,  Mumford,  Mosher,  Seabur-y,  Symon-House  and 
Gurney,  Ward,  Stirling,  Jardine,  Peterson,  Stevenson,  Yarrow, 
J.  Thorn,  Phillips,  Haythorn,  Shepherd.  Coil  Boilers — Fitch  and 
Voight,  Rumsey,  Seaward  and  Paul  (already  referred  to)— Boilers  of 
Gurney,  Dance  and  Field,  James,  Matheson,  Elder,  Ward,  Herreshoff, 
Thornycroft,  Craddock,  Lilienthal.  Cellular  Boilers — Mentioned  by 
Rumsey — Boilers  of  Teissier,  Hancock,  Church,  Brunton,  Anderson, 
McCurdy,  Zander,  Lamb  and  Summers,  Rowan  and  Horton, 
Panhard  and  Levassor.  Revolving  Boilers — Thompson  and  Barr's 
Boiler,  The  Pierce  Boiler.  Porcupine  Boilers — Boilers  of  Gibbs 
and  Applegarth,  Barrans,  Bougleux,  Fletcher,  Kennedy,  Clark — The 
Hazleton,  Minerva  and  "  Climax  "  Boilers.  Miscellaneous  Designs — 
Jacob  and  A.  M.  Perkins — Roberts  and  Almy  Boilers — Serpollet 
Boiler  —  Thornycroft  Boiler — De  Laval  Boiler  —  Simpson  and 
Bodman  Boiler.  Boilers  icitli  Gas  Producer  Arrangements — Boilers 
of  Church,  Johnson,  Sykes  and  Briggs,  Macfarlane  and  Coleman, 
Lilienthal  and  Bashall,  Taylor,  Thwaite  and  Watkinson — General 
Observations  on  Boiler  Designs. 

CHAPTER  IX. — SOME  TESTS  OF  BOILERS  AND  RESULTS         ...         510-602 

Selection  of  Results  Must  be  Made — Comparison  of  Boilers 
Requires  a  Large  Number  of  Details — Reference  to  Published 
Records  of  Boiler  Tests — Controversy  between  Advocates  of  Cylin- 
drical and  of  Water-tube  Boilers — Possibilities  of  Improvement  in 
Each  Case — Possible  Transmission  of  Heat,  Largely  a  Question  of 
Fire-Tubes  versus  Water-Tubes — Payne's  Early  Evaporative  Result 


xxiv  SYNOPSIS   OF   CONTENTS. 


— Mulhouse  Trials — Isherwood's  Trials — Flue  Tube  against  Water 
Tube — Craddock  Boiler  in  ss.  "  Thetis  " — American  Institute  Trials 
of  1871 — Howard  Boiler  Trials"  in  America — Allen  Boiler  Trials — 
Trials  of  Boilers  at  Philadelphia  Exhibition,  1876 — Diagram  of  these 
Results— Trials  at  Philadelphia,  1884— Fletcher's  Trials,  Water- 
tube  against  Lancashire  Boiler— Comparative  Weights  and  Space 
Occupied — Mr.  B.  Donkin's  Results  in  1895 — Marine  Boilers — Early 
Records  Defective — Results  with  Rowan  and  Horton  Boilers — 
Tables  of  Trials  of  More  Recent  Marine  Boilers — Trials  in  America 
— Trials  of  Thornycroft  Boiler  in  England — -Comparative  Trials  of 
Belleville  and  Scotch  Boilers  in  England — Milton's  Table  of  Results 
—Sir  J.  Durston's  Record  of  Trials  of  "  Seagull,"  "  Sheldrake,"  and 
"  Sharpshooter  " — Boilers  in  Recent  Cruisers — Particulars  of  Cylin- 
drical and  of  Water-tube  Boilers  in  British  Navy — Water-tube 
Boilers  in  the  French  Navy — D'Allest  Boiler — Xiclausse  Boiler — 
Records  of  Trials  in  the  German  Navy — Mosher  Boiler  Trial — Clyde 
Boiler  Trials— Muinford  Boiler  Trial— Haythorn  Boiler  Trials- 
Tests  of  Sinlpson  and  Bodman  Boiler — Comparison  of  Results — 
Weights  of  Various  Boilers  to  a  Standard  of  Comparison — Space 
Occupied  by  Various  Boilers,  Cylindrical  and  Water-tube  Types — 
Weights  per  Square  Foot  of  Grate  Area — Weights  of  Water 
Contained — Cost  of  Various  Boilers  in  French  Navy  till  1898 — 
Comparison  of  Average  Prices — Durability  of  Water-tube  Boilers — 
Records  of  Rowan  and  Horton,  Ward  and  Roberts'  Boilers— Pro- 
fessor Thurston's  Summary  of  American  Experience — Opinions  of 
Engineer-in-Chief  of  American  Navy,  Oct.,  1897,  and  Nov.,  1899— 
Durability  in  French  Navy-  Opinions  of  the  Author  and  Mr.  Milton 
— -Hudson's  Comparative  Tables  of  Results  of  Various  Trials  to 
Show  Heat  Utilization  and  Speed  of  Gases. 


THE   PRACTICAL   PHYSICS 


OF    THE 


MODERN    STEAM   BOILER. 


CHAPTER    I. 

INTRODUCTORY — GENERAL  CONSIDERATIONS. 

ALTHOUGH,  in  a  popular  view  of  the  subject,  the  water-tube 
boiler  is  considered  to  be  the  product  of  evolution  in  boiler 
design,  yet  this  is  true  only  as  regards  the  accepted  employment 
of  this  form  of  steam  boilers  for  marine  work.  Regarded  from 
the  point  of  view  of  design,  the  water-tube  (tubulous  or  sectional) 
boiler  is  one  of  the  earliest  products  of  engineering,  as  directed 
to  the  construction  of  steam  machinery.  It  rarely  happens  that 
the  originator  of  any  complete  form  of  apparatus  finds  the  ideas 
of  men  in  general  so  far  advanced,  or  their  minds  so  receptive, 
as  to  induce  them  to  adopt  at  once  a  new  thing,  the  principles 
of  which  they  have  not  grasped.  In  the  main,  ideas  must  rise 
from  what  is  elementary,  although  incomplete,  to  what  compre- 
hends a  larger  view  of  the  subject,  but  which,  although  it  may 
be  called  complex,  if  judged  superficially,  is  none  the  less  simple 
when  its  wider  range  of  principles  is  understood. 

From  very  early  days  in  the  history  of  the  steam  engine,  and 
of  engineering  as  connected  with  it,  there  have  been  instances  of 
men  who  have  sought  in  their  practice  to  carry  correct  prin- 
ciples of  physical  science  to  their  rational  conclusion.  Usually, 
however,  the  apprehension  of  principles  has  preceded  the 
existence  of  the  means  necessary  for  their  practical  application 
with  success — not  to  speak  of  the  general  readiness  of  men's 
minds  to  accept  them — and  engineering  has,  in  the  case  of 

B 


2  THE    PRACTICAL    PHYSICS   OF 

steam  boilers,  witnessed  at  least  one  example  of  this.  So  that 
these  early  attempts  to  reduce  science  to  practice  being  often 
unsuccessful,  general  practice  has  been  really  governed  more  by 
facility  of  construction,1  according  to  the  existing  state  of  appli- 
ances and  materials,  than  by  adherence  to  the  principles  which 
govern  the  working  of  the  apparatus  in  detail.  Doubtless  also, 
there  have  been,  and  are,  some  who,  pointing  to  the  failure  of 
early  examples  of  a  system  of  construction  which  is  correct  in 
theory,  and  to  the  comparative  success  of  types  more  simple 
and  rude,  have  argued  for  the  continuance  of  these  incorrect 
types  and  for  the  abandonment  of  efforts  to  arrive  at  a  successful 
application  of  true  principles.  But  the  law  of  progress  inhuman 
affairs  forbids  their  being  listened  to  beyond  a  certain  point,  and 
it  is  an  axiom  in  mechanical,  no  less  than  in  moral,  affairs  that 
magna  est  veritas  et  prcvvalebit. 

There  were,  almost  from  the  first,  two  distinct  fundamental 
ideas  upon  which  steam  engine  design  and  wrorking  were  based, 
and  consequently  two  distinct  schools  of  men  connected  with 
these  ideas  of  design.  The  one  school,  which  is  traceable 
through  Von  Guericke,  Huyghens,  Papin,  Newcomen,  Savery 
and  Watt,2  regarded  the  steam  engine  primarily  as  a  vacuum 
engine,  or  apparatus  by  means  of  which  the  pressure  of  the 
atmosphere  could  be  utilised,  and  the  other  school,  comprising 
Leupolcl,  Hornblower,  Heslop,  Bull,  Trevithick  and  Woolf, 
regarded  it  as  a  pressure  engine  or  apparatus  for  utilising  the 
expansive  force  of  steam  at  pressures  above  that  of  the  atmo- 
sphere. In  the  case  of  the  one  form  of  apparatus,  very  low 
pressures  of  steam  were  used,  the  main  portion  of  the  work 
being  done  by  atmospheric  pressures  acting  upon  one  or,  in  turn, 
both  sides  of  the  piston  ;  whilst  in  the  other  form,  the  steam 
propelled  the  piston  to  and  fro,  and  the  exhaust  took  place  at  a 
greater  or  less  pressure  above  that  of  the  atmosphere. 

In  spite  of  the  great  names  which  have  been  associated  with 
the  former,  it  is  more  in  connection  with  the  latter  that  the 
development  of  the  steam  engine  as  a  heat  engine  has  been 
found  to  proceed — although  the  compound  engine  to  some 

1  See  "A  Treatise  on  Steam  Boilers,  etc.,"  by  Robert  Wilson,    A.I.C.E., 
pages  3-5.    London,  Crosby  Lockwood  and  Co.,  1877. 

2  See  "  The  Steam  Engine  and  Its  Inventors,"  by  K.  L.  Galloway.    London, 
Macmillan  and  Co.,  1881. 


THE  MODERN  STEAM  BOILER.  3 

extent  combines  both  principles — and  it  is  the  development  of 
the  use  of  high  pressures  of  steam  which  has,  in  its  turn,  forced 
the  question  of  water-tube  boilers  to  the  front  and  their  general 
use  upon  the  serious  consideration  of  engineers. 

In  the  nature  of  the  case  difficulties  from  want  of  suitable 
materials  and  from  imperfections  of  manufacture  were  sure  to 
arise,  and  have  in  the  past  frequently  arisen  ;  but  in  our  days  both 
the  quality  of  materials  and  the  power  and  capability  of  machine 
tools  have  been  so  vastly  improved  that  less  difficulty  would  now 
be  experienced  in  constructing  boilers  to  work  at  a  pressure  of 
1,000  Ibs.  per  square  inch,  than  would,  at  the  beginning  of  the 
century,  have  been  met  with  in  producing  one  for  100  Ibs. 

The  ideas  familiar  to  men  in  general  have  also  progressed, 
and  it  is  an  undoubted  fact  that  the  subject  of  water-tube  boilers 
occupies  now  a  position  very  different  from  that  which  has  been 
generally  accorded  to  it  at  any  period  up  till  within  the  last  few 
years. 

As  late  as  the  year  1867,  one  writer  on  the  subject  said,  at  the 
close  of  an  interesting  paper,  l  "  experiment  daily  demonstrates 
that  there  is  no  insuperable  objection  to  the  water-tube  boiler, 
yet  comparatively  little  or  nothing  is  known  about  it  by 
engineers  or  boiler-makers,  and  although  the  author  believes 
that  the  principle  has  a  great  future  before  it,  the  subject  is  very 
far  indeed  from  having  as  yet  received  the  attention  it  deserves." 
That  remark  is  happily  not  applicable  now,  although  we  are  far 
yet  from  having  a  general  acceptance  amongst  engineers  and 
boilermakers  of  the  correctness  of  the  principles  on  which  the 
design  of  good  water-tube  boilers  should  be  based. 

Regarding  the  tardy  improvement  in  marine  boiler  design, 
Mr.  F.  J.  Bramwell,  speaking  after  compound  engines  had  been 
well  introduced  and  the  economy  arising  from  the  use  of  steam 
of  comparatively  high  pressure  used  expansively  was  well  estab- 
lished, remarked  in  1872, 2  that  he  had  been  "  often  struck  by 
the  indifference  with  which  for  so  many  years  the  constructors 
and  the  users  of  marine  steam  engines  regarded  the  question  of 
economy  in  fuel  ;  and  by  the  fact  that,  while  wonderful  progress 

1  "On  Water-Tube  Boilers,"  by  V.  Pendred, Trans.  Soc.  of  Engineers,  1867. 

2  Proceedings  of  the  Institution    of  Mechanical  Engineers,  Vol.  for  1872, 
pp.  125-154. 

B  2 


4  THE  PRACTICAL  PHYSICS  OF 

was  made  in  the  increase  of  the  speed  of  the  ships,  no  one 
seemed  to  care  about  the  quantity  of  fuel  burnt,  nor  to  look  upon 
excess  in  this  respect  as  a  stigma  on  the  profession  of  the 
mechanical  engineer.  So  far  as  the  marine  engineer  was 
concerned,  the  question  of  getting  this  economy  was  for  many 
years  beset  with  difficulties.  The  construction  of  the  marine 
steam  engine  employed,  and  the  form  of  boiler  with  it,  were 
inconsistent  with  attempts  at  economy.  The  boiler  was 
made,  not  so  much  with  a  view  to  strength,  as  with  the 
object  of  stowage  ;  and  thus  marine  boilers  became  huge 
rectangular  covered  tanks,  with  fireplaces  and  flues  all  having 
flat  sides,  because,  as  was  said,  '  that  figure  gives  the  greatest 
cubical  content  in  the  smallest  space.'  Although  engineers 
knew  that  the  cylindrical  shape  was  the  strongest,  yet  even  that 
form  was  not  for  a  long  time  introduced  into  steam  vessels, 
because  it  was  held  that  "the  most  convenient  form  of  the  boiler 
is  that  it  should  be  adapted  to  the  shape  of  the  boat,  and  that 
being  taken  for  granted,  the  safety  would  depend  upon  the 
strength  of  the  metal  and  not  on  the  form."  And  again,  "  The 
construction  of  marine  boilers  for  sustaining  the  higher  pres- 
sures of  steam  now  in  use,  is  a  subject  of  essential  importance 
for  efficiently  carrying  out  the  advantages  of  high  expansion 
in  compound  engines,  and  the  progress  of  their  application 
was  seriously  impeded  at  the  first  by  the  unsuitability  of  the 
boilers  in  use  at  the  time  for  carrying  the  higher  pressures 
required." 

In  1878, l  the  present  author  again  expressed  these  views, 
especially  with  reference  to  the  cylindrical  boilers,  which  had 
by  that  time  succeeded  the  "rectangular  tank"  form,  and  also 
pointed  out  in  what  respects  they  did  not  fulfil  several  conditions 
essential  to  an  efficient  steam  generator. 

Again,  in  1887,  the  late  Dr.  A.  C.  Kirk,  as  President  of  the 
Institution  of  Engineers  and  Shipbuilders  in  Scotland, 2  said,  on 
this  subject,  "So  far  as  we  have  gone  the  saving  effected  in  the 
weight  of  steam  used  to  produce  a  given  power  has  reduced  the 
total  weight  of  the  machinery,  although  the  scantlings  are 

1  "  On  the  Design  and  Use  of  Steam  Boilers,"  British  Association   Reports 
1878,  p.  712,  and  Engineering,  Vol.  xxvi.,  pp.  164  and  283. 

2  "Transactions  of  the  Institution  of  Engineers  and  Shipbuilders  in  Scotland," 
Vol.  xxxi.,  pp.  10,  ii. 


THE  MODERN  STEAM  BOILER.  5 

heavier.  From  what  we  have  seen,  not  only  has  there  been  a 
reduction  in  space  occupied,  and  in  the  weight  of  coal  and 
machinery,  but  there  has  been  a  saving  both  in  the  weight  and 
in  the  space  occupied  by  the  machinery  alone,  and  fewer  men 
are  required  to  work  it.  ...  As  to  the  future,  without  setting 
up  as  a  prophet,  I  may,  I  think,  venture  to  predict  that  it  is 
in  the  boiler  rather  than  in  the  engine  that  the  next  great 
step  will  be  made.  What  that  step  will  be  I  dare  not  venture 
to  foretell,  but  I  would  not  have  it  be  imagined  that,  because  the 
water-tube  boilers  of  the  '  Propontis '  gave  out  after  a  time,  the 
water-tube  boiler  cannot  be  revived. 

11  More  is  known  of  the  management  and  action  of  boilers  than 
was  known  then,  and  those  in  charge  have  learned  more,  with 
the  result  that  what  was  not  then  a  success l  may  contain  the 
germs  of  success  now.  I  commend  the  steam  boiler  to  the 
attention  of  all  my  hearers." 

Even  as  late  as  January,  1897,  we  find  the  author  of  a  paper 
on  "Suction  Draught"  for  boilers2  awaiting  "  the  advent  of 
some  more  commercially  successful  type  of  water-tube  boiler 
than  any  of  the  present  forms,"  and  thus  expressing  the  idea 
that  we  have  not  reached  the  limits  of  improvement  in 
boiler  design.  We  shall  endeavour  to  show  in  the  sequel  that 
there  are  solid  grounds  for  the  opinion  that  further  improvement 
is  possible. 

In  the  past  the  special  requirements  of  particular  work  have, 
or  the  duty  required  in  special  circumstances  in  practice  has, 
exercised  an  influence  in  developing  designs  in  certain  direc- 
tions. Thus  the  earliest  development  of  steam  carriages  for 
locomotion  on  roads  brought  into  existence  several  forms  of 
water-tube  or  sectional  boilers,  because  the  great  desiderata  for 
that  special  purpose  were  extreme  lightness  and  rapid  steaming 
power.  The  development  of  railways  and  the  conditions  under 
which  locomotives  work  on  them  have  created  for  us  the  distinct 
form  known  as  the  locomotive  boiler,  and  mercantile  steam 
navigation  has  called  forth  in  succession  the  "  rectangular  tank  " 

1  For  the  reasons  of  this  want  of  success  in  that  instance  the  reader  is 
referred  to  the  "  Transactions  of  the  Institute  of  Engineers  and  Shipbuilders 
in  Scotland,"  Vol.  xli.,  pp.  117-121. 

2 "  Transactions  Institute  Engineers  and  Shipbuilders  in  Scotland,"  Vol. 
xl.,  p.  107. 


6  THE  PRACTICAL  PHYSICS  OF 

boiler,  the  "  haystack  "  boiler  and  the  cylindrical,  "  drum  "  or 
"  Scotch  "  boiler,  whilst  the  requirements  of  ships  of  war  and 
especially  of  torpedo  craft,  have  recently  brought  forward 
various  forms  of  water-tube  or  sectional  boilers  with  mechani- 
cally produced  draught,  possessing  the  features  of  extended 
surface,  small  weight  per  indicated  horse  power,  and  great 
steaming  power. 

It  will  no  doubt  ultimately  be  found  necessary  to  go  outside  of 
and  beyond  such  requirements  of  special  conditions  of  work  in 
designing  boilers,  and,  as  led  by  the  results  of  investigation  into 
the  physical  conditions  under  which  transference  of  heat  and 
generation  of  steam  should  take  place,  to  proceed  on  the  basis 
of  a  more  intelligent  appreciation  of  physical  facts,  and  with 
more  complete  provision  against  loss  or  waste  of  the  energy 
which  we  wrish  to  employ  usefully,  than  has  been  possible 
hitherto.  Enquiry  into  the  phenomena  of,  and  investigation  of 
many  of  the  questions  connected  with,  the  action  of  steam 
boilers,  have  recently  been  prosecuted  with  considerable  vigour, 
and  it  is  to  be  hoped  that  the  outcome  of  such  research  will  be 
to  illuminate  a  larger  portion  if  not  the  whole  of  the  field  of 
boiler  action,  by  means  of  which  engineers  may  be  able  to 
understand  clearly  what  are  the  physical  conditions  for  which 
they  have  to  provide  in  designing  a  steam  boiler. 

The  kind  of  advice  usually  given  in  text-books  on  boilers  with 
reference  to  boiler  design  will,  it  is  also  to  be  hoped,  soon 
change,  and  instead  of  our  having  "  custom,  the  kind  of  water 
used,  and  the  cost  and  quality  of  fuel  in  a  given  locality,"  urged 
as  the  proper  factors  to  determine  the  kind  of  boiler  which 
should  be  used  there,  our  "  custom  "  will  rather  be  to  know  how 
to  treat  any  kind  of  water  and  any  quality  of  fuel  so  that  the  most 
economical  results  can  be  obtained  from  them  in  a  proper  form 
of  boiler.  We  are  sometimes  told  that  "  deviation  from  common 
practice  is  bad  and  should  be  made  only  for  sufficient  reasons," 
but  that  is  in  one  sense  bad  advice,  because  it  assumes  that 
common  practice  has  reached  the  summit  of  perfection,  instead 
of  its  being  itself  the  thing  which  constantly  needs  to  be  elevated. 
Such  advice  disparages  improvement  and  puts  an  inadequate 
and  really  pusillanimous  standard  before  young  engineers, 
tending  to  destroy  or  suppress  independence  or  originality  of 
thought,  and  to  teach  them  to  seek  ignoble  ease  under  the  safe 


THE  MODERN  STEAM  BOILER.  7 

shelter  of  a  popular  acceptance  of  erroneous  notions.  The  only 
sense  in  which  the  advice  should  be  adopted  is  that  in  which 
the  room  for  improvement  is  constantly  accepted  as  a  "  sufficient 
reason "  for  a  continuous  effort  to  "  deviate  from  common 
practice."  In  a  recent  work  on  Boilers  the  general  features 
which  are  to  be  looked  for  in  all  boilers  are  set  forth,  and 
we  are  told  that  whatever  may  be  the  type  of  boiler  chosen 
for  any  particular  work  or  locality  there  must  be  provided  the 
following  : — 

1.  Sufficient  grate  area  to  burn  the  fuel  required  under  the 
available  draught. 

2.  Suitable  combustion  space  to  properly  burn  the  fuel. 

3.  Sufficient  area  of  flues  or  tubes  to  carry  off  the  products  of 
combustion. 

4.  Sufficient  heating  surface  to  absorb  the  heat  generated. 

5.  Proper  water  space  to  prevent  too  great  a  fluctuation  of 
the  water  level  when  there  is  an  irregular  demand  for  steam. 

6.  Suitable  steam  space  to  prevent  too  great  a  fluctuation  of 
pressure  when  steam  is  taken  at  intervals,  as  for  the  cylinders 
of  a  steam  engine. 

7.  Sufficient  free  water  area  for  disengagement  of  steam. 
Such  a  statement  of  the  case  is,  however,  most  imperfect,  and 

the  omission  of  all  consideration  of  several  essential  elements  in 
boiler  design  and  working  renders  it  useless  except  under  the 
conditions  of  the  use  of  a  certain  kind  of  boiler. 

In  fact  the  authors  themselves  dismiss  most  water-tube  boilers 
as  unsuitable  on  these  grounds  :  "  The  last  three  conditions  are 
not  fulfilled  by  most  water-tube  boilers  ;  some  such  boilers 
depend  on  a  separator  for  disengaging  steam  from  water  "  ;  and 
evidently  the  only  good  water-tube  boilers,  according  to  this 
criterion,  would  be  those  which  depart  least  in  design  from  the 
cylindrical  or  other  tank  boilers. 

But  it  is  worth  considering  whether  under  altered  conditions 
such  a  summary  of  necessary  conditions  may  not  wholly 
disappear.  Thus  as  to 

i.  What  if  it  is  found  better  to  dispense  altogether  with  the 
existing  arrangement  of  grates  and  to  introduce  methods  of 
combustion  widely  differing  from  those  at  present  in  use  which 
necessitate  both  "  grates"  and  "  draught"  ?  Even  with  gaseous 
fuel  no  grate  would  be  required. 


8  THE  PRACTICAL  PHYSICS  OF 

2.  When  fuel  is  burnt  it  is  a  truism  that  there  must  be  suitable 
combustion  space  provided  for  the  operation,  but  we  are   not 
informed  in  the  statement  of  this  requirement  under  what  condi- 
tions the  fuel  is  to  be  burned,  and  therefore  it  follows  that  what 
might  be  suitable  in  one  method  of  combustion  would  be  quite 
unsuitable  for  another. 

3.  To  be  properly  stated  this  condition  should  have  informed 
us  at  what  velocity,  under  what  pressure,  and  at  what  tempera- 
ture the  products  of  combustion  are  to  be  carried  off,  as  these 
elements  would  cause  wide  differences  in  sizes  of  exits  wanted  ; 
and  similarly  in 

4.  We  should  be  informed  at  what  rate  the  heat  generated 
is  to  be  absorbed  by  the  heating  surface.     There   is   a  wide 
difference  in  this  matter  between  what  is  theoretically  possible 
and  the  best  that  has  as  yet  been  done  in  boilers. 

5.  As  to  this  we  need  to  ask,  "  fluctuation  "  where  ?  In  a  gauge- 
glass  or  column  outside  the  boiler,  or  in  the  boiler  itself  ?  The 
latter  evidently  is  meant,  but  our  ideas  of  a  large  surface  of  water, 
broken    only   by  the   appearance   of    bubbles   and  momentary 
upheavals  of  small  portions  of   the   surface,  are  quite  foreign 
to  what  is  no  doubt  proper  to  a  boiler  as  a  steam  generating 
machine,  in  which  the  essential  condition  is  that  the  whole  of 
the  water  in  the  boiler  should  be  kept  in  continuous  and  rapid 
motion. 

6  and  7  are  simply  corollaries  from  5,  and  if  they  do  not 
simply  mean  that  boilers  of  sufficient  size  to  supply  the  power 
needed  must  be  provided,  they  proceed,  as  does  5,  on  partial 
and  incomplete  views  of  what  proper  steam  generation  may 
require.  Why,  for  instance,  should  it  be  assumed  that  "free 
surface  "  (so-called)  is  better  for  disengaging  steam  from  water 
than  the  use  of  some  form  of  separator  ?  What  principle  that  is 
correct  is  in  action  where  "  free  surface  "  exists  that  cannot  be 
introduced  into,  or  employed  in,  a  separator  ?  It  is  evidently  a 
simple  question  of  counteracting  the  effects  of  rapid  motion,  so 
as  to  permit  of  the  action  of  gravity  which  causes  fluids  of 
different  specific  gravities  to  separate  from  one  another.  The 
"  free  surface,"  where  the  water  is  clean,  permits  the  operation 
of  the  action  of  gravity  to  take  place  in  one  way,  and  the 
separator,  when  it  is  an  efficient  one,  provides  for  that  action  in 
another,  but  not  necessarily  a  less  efficacious  way. 


THE  MODERN  STEAM  BOILER.  9 

At  present,  we  may  venture  to  assert  that  the  following  are 
demanded  from  a  good  boiler,  and  that  they  afford  a  criterion  by 
which  boilers  can  be  compared  and  judged  : — 

1.  The  maximum  of  heating  surface  in  proportion  to  weight. 

2.  The  maximum  of  strength  with   minimum  thickness  and 
weight  of  material. 

3.  The    maximum    of    strength    due   to   the   form    without 
artificial  support,  such  as  from  stays. 

4.  The  maximum  of  circulation  of  the  water  inside. 

5.  The  maximum  of  circulation  of  the  gases  outside. 

6.  The  maximum  of  transference  of  heat  from  the  gases  to  the 
water  per  unit  of  surface. 

7.  The  minimum  of  weight  in  proportion  to  steaming  power. 

8.  The  minimum  of  fuel  consumed  per  effective  horse  power. 

9.  The  minimum  of  water  delivered  with  the  steam. 

10.  The  minimum  of  heat  delivered  into  the  atmosphere. 
The  proof  of  these  things  will  come  up  in  detail  as  we  investi- 
gate the  subject,  and  we  shall  probably  get  an  approximate  idea 
of  the  best  that  is  possible,  by  means  of  which  we  can  institute 
a  fairly  true  comparison  between  rival  boiler  designs. 


CHAPTER    II. 
SOME  FUNDAMENTAL  ELEMENTS  OF  BOILER  DESIGN. 

THERE  are  certain  elements  of  boiler  design  which,  being 
fundamentally  necessary,  are  permanent  and  unaffected  by 
modiiications  which  may  require  to  be  introduced  as  certain 
physical  actions  or  lawrs  become  better  understood.  We  are 
plainly  concerned  with  the  laws  of  fluid  pressure  ;  with  those 
connected  with  steam  as  a  gas  which  requires  a  considerable 
expenditure  of  heat  for  its  formation  and  maintenance  at 
pressures  of  several  atmospheres,  at  which  it  is  capable  by  its 
expansion  of  producing  great  dynamical  effects,  and  these  must 
be  provided  for.  There  are  also  considerations  connected  with 
the  use  of  boilers  which  impose  some  necessary  conditions  on  all 
designs. 

Fluid  Pressure.  -  According  to  Pascal's  law  of  fluid 
pressure,  disregarding  the  effect  of  gravity,  the  pressure  is  trans- 
mitted uncliminished  in  all  directions,  and  acts  with  the  same 
force  on  all  equal  surfaces,  or  proportionally  to  the  area  of  the 
surface  of  any  part  of  the  internal  walls  of  the  vessel,  and  in  a 
direction  at  right  angles  to  the  surface.  In  the  case  of  cylindri- 
cal vessels  containing  fluid  under  pressure,  the  pressure  per 
square  inch  on  the  vessel  multiplied  by  the  number  of  inches  in 
the  circumference,  gives  the  total  stress  exerted  on  a  ring  of  the 
circumference  an  inch  wide. 

Strength  in  Relation  to  Form  and  Dimensions. — The  foregoing 
refers  to  pressure  exerted  radially  in  all  directions,  and 
is  not  to  be  confounded  with  the  measurement  of  the  force 
tending  to  split  the  cylinder  longitudinally.  As  to  this  latter,  it 
is  dealt  with  in  many  works  on  applied  mechanics,  and  on 
boilers.  Mr.  R.  Wilson  (in  "A  Treatise  on  Steam  Boilers, "London, 
1877),  for  instance,  says  that  the  force  tending  to  rupture  the  unit 
length  of  the  cylinder  of  a  boiler  longitudinally,  is  represented 
by  multiplying  the  diameter  by  the  pressure  on  each  unit  of 
surface.  The  total  amount  of  force  tending  to  divide  the  cylinder 
in  lines  parallel  to  its  axis  is  therefore  found  by  multiplying  the 


THE  MODERN  STEAM  BOILER.  n 

above  product  by  the  length  of  the  cylinder.  The  manner  in 
which  this  strain  is  borne  by  the  material  of  the  boiler  greatly 
depends  on  its  thickness.  "When  this  is  considerable,  compared 
with  the  diameter,  as  in  hydraulic  presses  and  cannon,  the  inner 
layers  of  the  material  are  more  severely  taxed  than  those  on  the 
outside.  This  difference  may  be  so  great,  that  the  latter  render 
no  material  assistance  to  the  former.  .  .  .  The  strength  of  a 
cylinder  to  resist  transverse  pressure  is  therefore  proportionate 
to  the  thickness  and  is  represented  by  the  tenacity  or  tensile 
strength  of  the  material,  multiplied  by  the  section  on  both  sides, 
or  twice  the  thickness  multiplied  by  the  length." 

It  is  easy  to  see,  therefore,  the  great  gain  in  strength  which  is 
obtained  by  reducing  diameters  and  thicknesses,  and  this  fact 
points  distinctly  to  the  fitness  of  water-tube  boilers  for  with- 
standing high  pressures. 

Another  advantage  that  is  gained  by  the  use  of  small  diameters 
is  that  as  there  is  less  departure  from  truly  circular  forms,  there 
is  less  opportunity  given  to  the  pressure  to  produce  deformation 
of  the  boiler.  Boilers  of  large  diameter  necessarily  depend,  for 
strength  to  resist  pressure,  to  a  considerable  extent,  upon  the 
material  of  which  they  are  constructed,  and  hence,  as  the  steam 
pressures  in  use  have  gone  up,  the  thicknesses  of  shell  plates 
have  also  advanced  as  far  as  possible  with  safety,  first,  with 
wrought  iron  and  then  with  steel  as  the  material.1  The  use  of 
this  thicker  material,  amongst  other  disadvantages,  causes  a 
greater  difference  in  diameters  between  the  various  rings  or 
longitudinal  portions  of  the  boiler  shell,  as  well  as  between  the 
shell  and  the  lap  or  butt  joints  in  it,  and  this  accentuates  the 
inequality  of  the  stresses  to  which  such  shells  are  subjected. 
This  subject  has  been  frequently  referred  to  in  works  on  boilers, 
but  seldom  in  more  clear  and  forcible  language  than  the  follow- 
ing2:— "  Emerson  showed,  more  than  sixty  years  ago,  that  the 
stress  tending  to  split  in  two  an  internally  perfectly  cylindrical 
pipe  submitted  to  the  pressure  of  a  fluid  from  the  interior,  is  as 
the  diameter  of  the  pipe  and  the  fluid  pressure.  He  also  showed 
that  the  stress  arising  from  any  pressure,  upon  any  part,  to  split  it 

1  See  on  "  Experience  in  the  Use  of  Thick  Steel  Boiler  Plate,"  by  William 
Parker.     Trans.  Inst.  N.A.,  1885. 

2  See  "  On  the  Wear  and  Tear  of  Steam  Boilers,"  by  F.  A.  Paget,  C.E. 
Jour.  Soc.  of  Arts,  London,  1865,  p.  388. 


12  THE  PRACTICAL  PHYSICS  OF 

longitudinally,  transversely,  or  in  any  direction,  is  equal  to  the  pres- 
sure upon  a  plane  drawn  perpendicular  to  the  line  of  direction. 

"  As  in  a  boiler  the  thickness  of  the  metal  is  small  compared 
with  the  radius,  the  circumferential  tension  has  been  assumed  to 
be  uniformly  distributed  ;  and  the  strain  per  unit  of  length  upon 
the  transverse  circular  joint,  being  only  half  that  upon  the  longi- 
tudinal joints,  the  strength  of  the  latter  has  been  taken  as  the 
basis  of  the  calculations  for  tensile  strength  of  the  joints.  But  in 
taking  the  internal  diameter  of  the  boiler  as  the  point  of  depar- 
ture, the  internal  section  has  been  assumed  to  be  a  correct  circle, 
which  would  only  be  practically  true  in  the  case  of  a  cylinder 
bored  out  in  a  lathe,  but  never  in  that  of  a  riveted  boiler.  Two 
of  Emerson's  corollaries  from  his  first  proposition  have,  in  fact, 
been  neglected.  He  showed  that  if  one  of  the  diameters  be 
greater  than  another,  there  will  then  be  a  greater  pressure  in  a 
direction  at  right  angles  to  the  larger  diameter  ;  the  greatest 
pressure  tending  to  drive  out  the  narrower  sides  till  a  mathe- 
matically true  circle  is  formed.  The  second  is,  that  if  an  elastic 
compressed  fluid  be  enclosed  in  a  vessel,  flexible  and  capable  of 
being  distended  every  way,  it  will  form  itself  into  a  sphere." 

The  strains  put  upon  the  shells  of  large  cylindrical  boilers,  such 
as  marine  boilers  of  the  il  Scotch  "  or  "  drum  "  type,  are  further 
complicated  by  the  insertion  of  furnaces  and  combustion 
chambers,  which  are  stayed  to  the  shell  and  ends  ;  and  there  are 
also  the  flat  surfaces  which  are  inseparable  from  boilers  of  large 
diameter  as  ordinarily  made,  and  must  be  stayed  together.  These 
latter  have  equal  pressure  upon  them  only  when  these  surfaces 
are  equal,  but  this  they  very  seldom  are,  and  consequently  there 
is  an  opportunity  presented  in  their  existence  for  the  action  of 
unequal  pressure  producing  further  deformation. 

Deformation,  Changes  due  to  Pressure.  —  Some  measure- 
ments of  the  actual  amount  of  deformation  of  Scotch  or 
cylindrical  boilers  observed  at  both  working  pressure  and 
test  pressure  have  been  published  by  Mr.  J.  T.  Milton,1 
Chief  Engineer-Surveyor  to  Lloyd's  Registry,  and  these  show  the 
extent  of  the  deflections  to  be  in  general  in  direct  proportion  to 
the  pressure  applied,  "  being  at  the  test  pressure  about  twice 
that  at  the  working  pressure." 

1  "  Notes  on  some  Alterations  of  Form  to  which  Boilers  are  Subject  when 
under  Working  Conditions,"  Trans.  Inst,  N.A.,  Vol.  xxxiv.,  1893,  p. 157. 


THE  MODERN  STEAM  BOILER. 

TABLE   I. 


Boiler  A. 

Boiler  B. 

Boiler  C. 

Diameter  of  boiler  (mean) 
Length  of  boiler 
Working  and  test  pressures   ... 
No.  and  description  of  furnaces 
Diameter  of  furnace  (outside) 

14  ft.  i  in. 

10  ft. 

160  Ibs.  320  Ibs. 
3  Purves. 
3  ft-  3  in. 

15  «. 
9  ft.  9  in. 
80  Ibs.        160  Ibs. 
3  plain. 
3  ft.  6  in. 

15  ft-  3  in. 

17  ft. 
160  Ibs.      320  Ibs. 
6  Fox. 
3  ft.  n  in. 

Length  of  furnace,  over  tube 

plates 

7ft. 

6  ft.  6  in. 

6  ft.  8  in. 

No.  of  combustion  chambers 

in  boiler    ... 

3 

3 

3  each  common  to 

No.  of  vertical  rows  of  stays  in 

2  furnaces. 

sides  of  chambers  ... 

2 

2 

4 

Thickness  of  shell  plates 

ij  in. 

Mm- 

i  JJ  in. 

Thickness    of    chamber    side 

plates 

!§  in. 

Jin. 

fin. 

Thickness  of  chamber  bottom 

plates 

I  to. 

Jin. 

gin. 

Thickness  of  furnace  plates   ... 
Chamber  tops  stayed  by 

M  in. 
Girders. 

Jin. 
Curved. 

Kin. 

Girders. 

Chamber  bottoms     ... 

Not  stayed. 

Stiffened  with  J.  not 

i\ot  stayed. 

connected  to  shell. 

OBSERVED  ALTERATIONS  OF  DIMENSIONS. 

At  working 

At  test 

At  working 

At  test 

At  working 

At  test 

pressure  of 

pressure  of 

pressure  of 

pressure  of 

pressure  of 

pressure  of 

160  Ibs. 

320  Ibs. 

80  Ibs. 

160  Ibs. 

160  Ibs. 

320  Ibs. 

Decrease   of    horizontal    dia- 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

Inch. 

meter  of  shell 
Increase  of  vertical  ... 

0 
ft 

t 

O 
& 

t, 

i 

¥ 

DECREASE  OF  WIDTH  OF 

CENTRE  OF  COMBUSTION 

CHAMBER  :— 

(i)  At  level  of  centre  of  boiler. 

Near  back   plate    (boiler  C 

near  tube  plate)  ... 

A 

A 

O 

rV 

3^5 

At  centre  ... 

o 

5*5 

3\ 

iV 

3*3 

Near  tube  plate 

A 

iV 

n 

3s 

n 

(2)  At  narrowest  part. 

Near  back  plate  (boiler  C 

near  one  tube  plate) 
At  centre  ... 
Near  tube  plate 
(3)  At  springing  of  cylindrical 

iv 

f 

A 

I 

f 

1 

part  of  bottom. 

Near  back   plate  (boiler  C 

near  one  tube  plate) 

o 

A 

o 

o 

/a 

At  centre  ... 

A 

iV 

0 

3^2 

• 

,^'j 

Near  tube  plate 

A 

5\ 

A 

iV 

& 

s7* 

DECREASE  OF  WIDTH  OF 

STARBOARD  CHAMBER  :— 

(i)  At  level  of  centre  of  boiler. 

Near  back   plate  (boiler  C 

near  one  tube  plate) 

o 

A 

o 

O 

o 

tV 

At  centre  ... 

o 

0 

o 

0 

"tV 

T^J 

Near  tube  plate 

A 

TV 

A 

A* 

A 

n 

(2)  At  springing  of  cylindrical 

part  of  the  bottom. 

Near  back  plate  (boiler  C 

near  one  tube  plate) 

o 

0 

o 

& 

tV 

j 

At  centre  ... 

o 

O 

o 

0 

iV 

A 

Near  tube  plate 

o 

o 

0 

A 

ft 

1 

DECREASE  OF  WIDTH  OF 

PORT  CHAMBER:— 

(i)  At  level  of  centre  of  boiler. 

Near  back  plate  (boiler  C 

near  one  tube  plate) 
At  centre  ... 
Near  tube  plate 

0 

A 

i 

A 

A 

I 

i 

A 

1 

(2)  At  springing  of  cylindrical 

part  of  bottom. 

Near  back  plate  (boiler  C 

near  one  tube  plate) 

£f 

3^1 

o 

0 

0 

A 

At  centre  ... 

0 

0 

Ay 

3*2 

A 

? 

Near  tube  plate 

A 

A 

* 

% 

& 

A 

*  This  indicates  a  slight  return  movement. 


THE  PRACTICAL  PHYSICS  OF 


4 

1 

d     1     ?f  -d      P 

f 

OBSERVED  ALTERATIONS  OF  DIMENSIONS. 

«£* 

«is 
<  s  ° 

i-     .-2                     -s 

v3"P,          :  fj.       :   :   :       :   •    •   :             «o 
ffS             ^                                            i 

.III 

IP 

d.S            .5 
-«           i-g       :   :   :       :    :    I    I               : 
^             i 

Boiler  K. 

i          '.   41 

0         0         d  .5                               C.cCen 

^!l1!i!ir§     * 

|      *     """      el*      - 

III 
ill 

e."" 

c-5'           --                          -                      d 

z,g     :^           :*:  :      i 

Hi 

"Hi 

II      ^iim        i 

i 

5                     E§ 
.5.5°     8    .S.S         '     .JjUJe                 1, 

«;  1  ss  1  ii^H 

""3  *  w*  III  ,""  -            § 

At  test  pressure 
of  320  Ibs. 

.  c    .          ^  ^    - 

J 

II            Id        & 

1 

a-  5  -    «*    g|3            j~          | 
£                   •£              H 

At  test  pressure 
of  350  Ibs. 

H?                A 

K 
1 

js                               ing 

Li  !  ii  ,  ,^{$1    f, 

f|  £  3  '    'JWSjIl,    1' 

At  test  pressure 
of  300  Ibs. 

«   :           i    =       :   :   :       :    :   :   i             J 
£                                                                 ^ 

Boiler  G. 

JiiJ!s§:,f!l 

iN 
iW 

?R       £3     '•  '•  '•      '•  '•  '•  '•           R 
*S      ^^>                                A> 

ff&l  £  d*  Lr     fiVPil 

5     °     M        gll                 |c|M||5 

•   £                       -5>                i 

III 

<lii 

d.S        .S.S                                          .5 
—  o          w  *      i   :   :       :   :   :   :             o 

fa 

i 

j                   £§                   ^5             IS 
S            •        8~                   c"0             "5  -2- 

d^    |    ^    1S||JJ|^J1             'Ml 

S"^  oi      *      ~  z      v      <J  .0  H*«W  7  71  ™-  8*                 S     -S 

^           w-o     „-  §  £  "        «"»  S  2  =5          1    « 

5               a  E  5            "E  ^-s        a  =  ?. 

£                        S______| 

ssJ 

5|8 

**°                            ^  »o  in      iC                             i 

|S^ 

IP 

c  d  .=      c 

H 
| 

1 

J!                 l!                                Is 

g  s  s              L 

-i     M"  jil  M    -^         11 

III 
«il 

d            .5         -S            .S                       .5 
"**            K         «             S                      ^ 

.||| 

"IB 

dec                          d 
•S   :          «  {     «  J  i     «  •{  H             '^ 

•*»      8x5          ^, 

Q 
1 

i-8    .S      ..S     «        odd  •  • 

«j  4  S5  1     !3?^ 

1  1 

At  Test  Pressure 
of  300  Ibs. 

ii  g-;i..-..V:    i 

:       1.2:       :S.S         |           :i                                                                    "3    •=  &  o   •  6  1   i   i   :  oVu   i   i  g  S.%    \ 

18       !u2      ^       ii                                         S  !-s|sl5|j  iilf^  i  if- 

=       :|           :«^         -S           ij                                                                    |   i'sgc'SrtS   :    :   :ag«   :    i^^  _o 

4  ^  i?i  i  ii      ^         «  u'iil  J  uj  •  HI 

I:    i  :    *  !!5.f       I              silMIIiljJiSJi^ 

r   s-I      ?«-.§      S   ^1   51                                  I  ST^H  Ull'stlJsW 

nit  in  yiii    i 

•s-°§-s      °^s     --E|O=  =  --O           s                     o  ;.r'Bs^si££ri5«j!s-o^-5. 

!i!i|lHa===!      1 

.aS.°d-o     .Sgd^      602                                                                            SJ-S  b  jj  =  ^  d  6  S.^;>5  d  ^6^^  b  "S  5  U 
«0^>5          0^^          ^IHO                       U                                           Q=QGaQG           = 

THE  MODERN  STEAM  BOILEtf.  15 

These  observations  are  given  in  Tables  I.  and  II.,  and  the 
designs  of  boilers  to  which  they  refer  are  shown  in  the  outline 
diagrams,  Figs.  I  to  5. 

Mr.  Milton  remarked  that  "  in  designing  boilers,  the  require- 
ments of  strength  are  generally  supposed  to  be  fully  met  by 


FIG.   3. 

considering  the  cylindrical  shell  to  be  in  perfect  equilibrium  under 
the  uniform  internal  pressure,  which  produces  a  tensional  stress 
in  the  shell  plating  proportional  to  the  pressure  and  to  the 
diameter  of  the  boiler.  The  furnace  flues  are  cylindrical  in  form 
and,  together  with  the  cylindrical  portions  of  the  combustion 
chamber  bottoms,  are  supposed  to  be  in  equilibrium  under  the 


16  THE  PRACTICAL  PHYSICS  OF 

uniform  external  pressure  and  the  compressive  stress  it  produces 
in  the  plates  ;  while  the  flat  parts  of  the  boiler  are  supposed  to 
be  perfectly  supported  by  the  stays.  In  practice,  however,  there 
are  several  considerations  which  lead  to  departures  from  the 
simple  conditions  above  alluded  to,  and  it  is  in  consequence  of 
these  that  the  deformations  of  the  different  parts  take  place. 
The  most  important  of  these  changes  of  form  are  the  variations 
of  the  transverse  dimensions  of  the  combustion  chambers,  and 
the  alteration  of  shape  of  the  cylindrical  shell.  Considering  the 
latter  first,  it  is  evident  at  once  that  the  cylindrical  shell  will  be 
in  equilibrium  if  it  is  truly  circular  in  shape,  and  is  subjected  to  a 
uniform  internal  pressure,  but  to  no  other  forces.  If,  however, 
it  is  acted  upon,  in  addition  to  the  pressure,  by  other  forces  not 
uniformly  distributed  round  the  circumference,  the  equilibrium 
will  be  destroyed,  and  an  alteration  from  the  truly  cylindrical 
form  must  take  place.  In  most  boilers  these  latter  conditions  hold. 
The  sides  of  the  wing  combustion  chambers  are  stayed  to  the 
shell,  as  shown  in  Fig.  I  and  unless  the  staying  is  continuous 
round  the  crown  and  bottom  of  the  boiler,  as  in  Figs.  2  and  3, 
the  pull  of  the  stays  must  distort  the  boiler,  lessening  its 
horizontal  and  increasing  its  vertical  diameter. 

"  Next,  consider  the  flat  surfaces.  If  two  equal  surfaces  be 
tied  together  by  stays  and  be  subjected  to  equal  pressures  in 
opposite  directions,  they  will  be  in  equilibrium,  and  the  stress  in 
the  stays  may  fairly  be  taken  as  equal  to  the  total  pressure  on 
either  of  the  surfaces.  If,  however,  unequal  surfaces  are  stayed 
together,  and  are  subjected  to  equal  intensity  of  pressure,  it  is 
evident  that,  the  load  on  the  larger  surface  being  greater 
than  that  on  the  smaller,  the  smaller  surface  cannot  produce 
supporting  forces  in  the  stays  sufficient  to  prevent  all  yielding, 
and  deformation  will  occur,  the  stays  moving  in  the  direction  of 
the  larger  surface,  which  will  bulge  outwards,  while  the  smaller 
surface  will  be  drawn  inwards  against  the  pressure  by  the  stays. 
An  illustration  of  this  is  shown  in  Fig.  4,  which  represents  the 
horizontal  section  of  a  double-ended  boiler  with  six  furnaces  and 
three  combustion  chambers.  The  area  of  the  front  tube  plate  is 
greater  than  the  combined  areas  of  the  three-back  tube  plates. 
They  are  tied  together  by  the  tubes,  and  when  under  pressure 
the  front  tube  plate  bulges  outwards,  drawing  the  back  tube 
plates  with  it,  as  shown  exaggerated  by  the  dotted  lines. 


THE  MODERN  STEAM  BOILER.  17 

"  Coming  to  the  sides  of  the  combustion  chambers,  we  have 
those  nearest  to  the  shell  plates  connected  to  the  shell  by  stays. 
The  pressure  on  the  chamber  side  plates  would  cause  them  to 
bulge  inwards  if  there  were  no  stays  ;  the  tendency  to  bulge  pro- 
duces a  tension  in  the  stays  which,  as  we  have  seen,  distorts  the 
shell  from  a  truly  cylindrical  form.  This  yielding  of  the  shell 
must  be  accompanied  by  a  yielding  of  the  chamber  sides,  which 
accordingly  become  curved  inwards. 

"  If  we  now  consider  the  chamber  as  a  whole,  we  see  that  as 
the  pressure  on  the  side  a  b  (Fig.  4)  is  exactly  equal  to  that  on 
the  side  c  d,  the  total  forces  exerted  by  the  stays  on  the  side  c  d 
must  also  be  equal  to  the  total  forces  exerted  by  the  stays  on  the 


I    I   I 


FIG.  4. 

side  a  b.  The  difference  between  the  total  pressure  on  either 
side  and  the  forces  exerted  by  the  stays  on  that  side  must  be 
borne  by  the  tube  plates  a  c  and  b  d,  which  will  be  put  into 
compression.  The  sides  e  f  and  c  d  must  be  under  nearly  the 
same  conditions  of  load  and  support  as  the  side  a  6,  and  there- 
fore their  deformation,  if  any,  under  these  conditions,  must 
practically  be  the  same  as  that  of  a  6,  so  that  all  three  chambers 
will  be  nearly  equally  deformed.  The  stays  in  the  water  spaces 
are  practically  unaltered  in  length,  so  that  the  diminution  of 
horizontal  diameter  of  the  shell  will  produce  a  collapse  or 
narrowing  of  each  of  the  chambers  equal  to  about  one-third  of 
the  alteration  of  diameter. 

"  It  will  be  seen  from  the  Tables  that  the  greatest  alteration 


i« 


THE  PRACTICAL  PHYSICS  OF 


which  takes  place  is  in  the  horizontal  width  of  the  combustion 
chambers,  at  about  the  level  of  the  centre  of  the  wing  furnaces. 
Fig.  5  shows  a  section  of  the  boiler  at  this  part.  The  wing 
chamber  plates  at  about  this  level  are  parts  of  cylindrical 
surfaces,  and  if  there  were  no  stays  fixed  to  them  they  would 
retain  their  form  when  the  boiler  was  subjected  to  pressure. 
Evidently  then,  if,  in  addition  to  the  pressure,  they  have  forces 
acting  on  them  produced  by  the  pull  of  the  stays,  they  must 
alter  in  form,  yielding  in  the  direction  of  the  pull,  the  case  being 
similar  to  that  of  the  shell  plating  acted  on  by  the  pull  of  the 
side-stays.  If  any  yielding  takes  place  in  this  direction,  the 
side  plating  of  the  centre  chamber  must  become  equally 


FIG.  5. 

distorted,  and  the  Tables  show  that  in  some  cases  the  narrowing 
of  the  centre  chamber  produced  by  this  distortion  is  nearly  a 
quarter  of  an  inch  at  the  working  pressure,  and  as  much  as  half 
an  inch  at  the  testing  pressure.  The  yielding  of  the  wing 
chamber  side  plating  is,  of  course,  of  equal  amount  to  that  of 
the  plating  of  the  centre  chamber  ;  but  as  it  is  outwards  at  this 
side,  while  the  plating  at  the  other  side  yields  inwards,  the 
width  of  the  wing  chambers  at  this  part  is  not  so  much  altered, 
and  the  straining  action  is,  therefore,  somewhat  masked. 

"  It  is  to  be  also  noticed  that  in  the  side  chambers,  the  plating 
being  continuous  at  this  part  with  the  furnaces,  the  deformation 
referred  to  will  take  place  without  producing  severe  local 
stresses,  but  in  the  centre  chamber  at  this  level  the  tube  plates 


THE  MODERN  STEAM  BOILER.  19 

prevent  any  yielding  of  the  side  plating  adjacent  to  them,  and  it 
scarcely  needs  pointing  out  that  the  deformation,  being  of  the 
extent  above  mentioned  at  the  centre,  and  nearly  as  much  at 
the  end  stays,  but  practically  nothing  at  the  tube  plate  ends, 
must  put  a  severe  local  strain  on  the  plates,  especially  if  the 
staying  is  close  to  the  tube-plate  flange." 

Mr.  Milton  does  not  seem  to  have  included  in  his  observations 
any  measurement  of  deformation  of  the  boiler  shell  due  to  the 
opening  made  in  it  for  the  steam  dome  and  to  the  form  of  the 
steam  dome,  or  any  measurement  of  alteration  of  form  in  the 
steam  dome  itself  under  pressure.  Yet  it  is  undoubted  that 
these  have  been  in  the  past  serious  causes  of  weakness,  and  even 
of  danger,  as  explosions  such  as  those  in  the  steamers 
"Marcasite  "  and  "  Renown  "  long  ago  proved.1 

Now,  although  it  is  to  be  remarked  that  these  alterations  of 
form  which  are  recorded  in  Mr.  Milton's  Tables  are  not  severe 
enough  in  general  to  produce  a  permanent  set,  even  at  the  test 
pressures,  and  that  in  spite  of  the  existence  of  such  alterations 
many  boilers,  which  are  from  their  design  subject  to  them,  have 
continued  in  successful  work  for  years,  so  that  these  deforma- 
tions are  not  in  themselves  dangerous  so  long  as  boilers  are 
constructed  of  material  of  good  ductile  quality,  yet  "  their 
extent  indicates  the  necessity  for  using  material  possessing  a 
very  high  degree  of  ductility,  and  for  so  designing  the  details  of 
the  construction  that  the  inevitable  deformations  may  take  place 
without  producing  severe  local  strains." 

Oscillatory  Strains — Fatigue  of  Metals. — It  must  be  borne  in 
mind  also  that  iron  and  steel  become  deteriorated  in  ductility 
by  a  frequent  repetition  of  strains  which  are  individually  much 
less  than  the  stress  which  would  produce  sudden  fracture  or 
permanent  set,  and  therefore  in  this  view  it  might  even  be 
better  for  boilers  if  the  test  pressure  produced  once  for  all, 
as  a  permanent  set,  the  maximum  alteration  of  form  due  to  the 
pressure. 

This  subject  of  the  effect  of  repeated  or  oscillatory  strains,  to 
which  the  name  of  the  "  fatigue"  of  metals  was  given,  was  very 
carefully  investigated  several  years  ago  by  M.  Wohler,  the 
chief  Engineer  of  the  Niederschlesisch-Markische  Eisenbahn 

1  See  an  article  entitled  "  The  Recent  Marine  Boiler  Explosions,"  by  F.  J. 
Rowan,  published  in  The  Anglo-Australasian^  London,  1875. 


20  THE  PRACTICAL  PHYSICS  OF 

in  Prussia,  and  in  addition  to  M.  Wohler's  papers,  published  in 
"Erkbam's  Zeitschrift  fur  Bauwesen "  for  1858,  1860,  1863, 
1866,  and  1870,  the  Prussian  State  Railway  exhibited  at  the 
Paris  Exhibition  in  1867  sketches  of  the  ingenious  testing 
machines  constructed  by  M.  Wohler  for  this  work,  and  also 
specimens  and  results  of  his  various  tests.  A  very  interesting 
account  of  these  experimental  researches  was  given  by  the  late 
Mr.  Ferdinand  Kohn  in  his  book  on  "  Iron  and  Steel  Manu- 
facture,'' l  and  on  M.  Wohler  relinquishing  the  work,  it  .was 
carried  on  by  Prof.  Spangenberg  and  others.  Results  also 
obtained  by  Sir  W.  Fairbairn,2  by  Prof.  Knut  Styffe3  at  Stock- 
holm, by  M.  Josef  von  Stummer-Traunfels,4  Engineer  of  the 
Northern  Railway  of  Austria,  and  other  investigators  of  the 
elasticity  of  metals,  abundantly  confirmed  the  correctness  of 
M.  Wohler's  deductions.  These  may  be  briefly  stated  as  follows  : 
(i)  Fracture  may  be  produced  by  the  continual  repetition  of 
oscillating  stresses,  all  of  them  much  below  the  breaking  stress. 
It  is  the  differences  of  strain,  defined  by  the  extent  of  the 
oscillations  which  then  produce  fracture.  (2).  The  absolute 
value  of  these  stresses  only  enters  into  the  question  so  far  that 
the  greater  this  value  the  smaller  are  the  differences  which  will 
finally  produce  fracture.  Short  of  producing  fracture  (though 
continuing  up  to  the  point  of  fracture)  considerable  changes  in 
the  molecular  structure  of  the  metal  are  produced  by  the 
"  fatigue."5 

Professor  Spangenberg's  investigations  confirmed  Wohler's 
law,  and  his  enquiries  into  the  connection  between  the  appear- 
ance of  fractures  and  the  molecular  changes  produced  in  the 
material  broken  by  repeated  strains,  showed  that  the  crystalline 
form  was  gradually  changed  to  the  amorphous.  Thus  arise 

1  Published  by  William  Mackenzie,  Glasgow,  in  1869,  pages  245-249.     See 
also  Min.  Proc.  Inst.   C.E.,  Vols  lx.,  415  (containing  an  abstract  of  paper  by 
Prof.   L.  Spangenberg,  published   in  Glaser's    "  Annalen  fur  Gevverbe  und 
Bauwesen,"  Vol.  v.  p.  6),  Ixiii.,  276-278,  and  Ixiv.  283  ;   Engineering,  Vols. 
iv.  p.,  160,  and  xi.  p.,  199,  etc. 

2  British  Association,  1867. 

3  "  The   Elasticity   of    Iron   and   Steel,"   by  Knut   Styffe.     London  :   John 
Murray,  1869. 

4  F.  Kohn,  "  Iron  and  Steel  Manufacture." 

5  "  Professor  Thurston's  Manual  of  Steam  Boilers  "  seems  to  be  the  only 
work  on  Boilers  which  includes  this  action  in  the  consideration  of  the  strength 
of  boilers, 


THE  MODERN  STEAM  BOILER.  21 

different  states  of  equal  density  of  the  molecules,  each  state 
having  its  own  limit  of  elasticity.  Professor  Spangenberg  tested 
the  molecular  theory  by  means  of  experiments  on  the  velocity  of 
conduction  of  sound  in  the  bars  by  Kundt's  method,  and  found 
corroborative  results. 

Causes  of  Oscillatory  Strains. — In  boilers  several  causes  com- 
bine, where  deformation  is  possible,  to  produce  the  repeti- 
tion of  strains  or  oscillating  stresses,  and  there  are  not 
wanting  proofs  of  their  effects  on  the  molecular  structure 
of  the  material.  (i)  One  of  these  causes  is  the  frequent 
raising  and  lowering  of  the  steam  pressure,  not  only  at  the 
commencement  and  end  of  a  voyage  or  period,  when  steam 
is  first  got  up,  and  when  the  pressure  is  wholly  released 
in  the  boiler,  but  also  at  the  various  stoppages  or  interrup- 
tions during  its  course,  and  even  in  the  lesser  fluctuations 
of  pressure  from  hour  to  hour,  or  from  watch  to  watch, 
according  to  the  state  of  the  fires.  A  graphic  log,  such  as  that 
brought  forward  by  Mr.  Robert  Caird  and  Mr.  G.  Gretchin  in 
"  The  Transactions  of  the  Institution  of  Engineers  and  Ship- 
builders in  Scotland  "  (Vol.  xli.,  p.  155),  might  give  a  complete 
record  of  such  fluctuations  of  pressure,  but  few,  if  any,  such 
records  have  been  published  as  yet.*  (2)  Again,  in  working, 
the  pulsatory  delivery  of  steam  to  the  engines  has  been  proved 
to  produce  a  gentle  undulation  or  "  breathing  "  action  which, 
though  small,  cannot  be  considered  insignificant  on  account  of 
its  frequency,  being,  as  it  is,  synchronous  with  the  number 
of  strokes  of  the  piston  per  minute. 

Mr.  F.  A.  Paget,  in  the  paper  already  quoted,  remarked, 
"  According  to  Dr.  Joule,  the  mere  dead  pressure  of  an  elastic 
fluid  is  due  to  the  impact  of  its  innumerable  atoms  on  the  sides 
of  the  confining  vessel.  When  the  motion  of  a  current  of  steam 
is  suddenly  checked,  as  by  the  valve,  in  its  passage  from  the 
boiler  to  the  cylinder,  its  speed  and  weight  cause  a  recoil  on  the 
sides  of  the  boiler  analogous  to  the  effects  of  the,  in  this  case, 
almost  inelastic  current  of  water  in  the  hydraulic  ram.  This 
action  is  necessarily  most  felt  with  engines  in  which  the  steam 
is  let  on  suddenly,  as  in  the  Cornish  and  other  single-acting 
engines,  working  with  steam  valves  suddenly  affording  a  wide 
outlet,  and  as  suddenly  closing.  It  produces  such  phenomena 
as  the  springing  or  breathing  of  cylinder  covers,  and  the  sudden 


22 


THE  PRACTICAL  PHYSICS  OF 


oscillations  of  gauges,  noticed  long  ago  by  Mr.  Josiah  Parkes 
and  others."1  "The  intensity  of  the  instantaneous  impulses 
thus  generated  would  be,  as  Mr.  Parkes  observes,  difficult  to 
measure,  but  their  repeated  action  must  rapidly  affect  the  boiler 
at  its  mechanically  weakest  points.  The  more  or  less  sudden 
closing  of  a  safety-valve  while  the  steam  is  blowing  off  would 
evidently  produce  the  same  effect.  .  .  .  But  there  can  be  little 
doubt  that  most  boilers  are  subjected,  sooner  or  later,  to  an 
impulsive  load." 

It  is  well  understood  that  the  effects  called  "  grooving  "  are 
due  in  the  first  place  to  such  repeated  actions,  which  not  only 
deteriorate  the  molecular  constitution  of  the  metal,  but  otherwise 


FIGS.  6  AXD  7. 

assist  local  oxidation  and  corrosion.  Figs.  6  and  7  illustrate  the 
forms  which  joints  tend  to  assume  under  the  influence  of  steam 
pressure  in  the  boilers,  and  Figs.  8,  9,  and  10  different  appear- 
ances of  the  effects  produced  by  grooving.  Many  explosions 
of  boilers,  especially  those  of  locomotives,  have  been  traced  to 
this  cause. 

Strains  due  ic  Heating. — (3)  Another  source  of  repeated  strains 
in  boilers  is  found  in  the  application  of  heat  and  in  the  forces 
produced  by  expansion  and  contraction  of  the  material  of  which 
the  boiler  is  constructed.  In  an  ordinary  Scotch  or  cylindrical 
marine  boiler  with  internal  furnaces,  there  are  two  portions  of 
the  boiler  which  are  particularly  exposed  to  considerable 

1  Min.  Proc,  Inst.  C.  E.  Vol.  iii. 


THE  MODERN  STEAM  BOILER.  23 

differences  of  temperature  in  working,  in  consequence  of 
which  these  parts  have  to  endure  the  strains  produced  by 
unequal  expansion.  These  parts  are  the  furnace  tubes  and  the 
boiler  shell. 


FIGS.  8,  9  AND   10. 

In  the  case  of  a  furnace,  according  to  one  good  authority, 
"  the  portion  above  the  fire,  especially  when  coated  with  even 
the  thin  enamel  of  scale  which  is  necessary  to  preserve  it  from 
corrosion,  must  be  considerably  hotter  than  the  portion  below 
the  bars.  Hence  the  top  of  the  furnace  tends  to  get  longer  than 
the  bottom.  If  the  end  fastenings  of  the  furnace  were  so  rigid 


24  THE  PRACTICAL  PHYSICS  OF 

as  to  maintain  the  top  and  bottom  of  the  same  length,  the  top 
would  have  to  be  compressed  and  the  bottom  stretched,  and 
every  difference  of  a  degree  Fahrenheit  in  the  temperature 
would  produce  a  compressive  stress  in  the  top  and  a  tensile 
stress  in  the  bottom  of  93  Ibs.  per  square  inch.  But,  actually, 
the  end  fastenings  are  not  so  rigid,  and  the  strains  caused  by  the 
unequal  expansion  are  not  distributed  from  top  to  bottom  by 
the  ends  only,  but  also  in  a  great  measure  by  the  resistance  to 
shear  of  the  plate,  and  hence  the  greatest  stresses  come  at  the 
middle  of  the  length  of  the  furnace.  Also  it  is  evident  that  these 
strains  are  not  uniformly  distributed,  and  hence  their  maximum 
must  be  greater  than  their  mean,  and  with  a  great  difference  of 
temperature  the  stresses  reach  a  high  figure.  Now,  by  putting 
rings  in  the  furnaces,  the  whole  strain  on  the  plate  has  to  be 
borne  by  the  reduced  sectional  area  through  the  rivet  holes,  or 
at  the  parts  which  are  weakened  by  flanging  when  Adamson's 
ring  is  used,  and  in  these  instances  the  rings  have  made  the 
furnaces  actually  weaker  than  they  were  before,  although  their 
object  is  to  strengthen  them.  In  one  steamship  a  number  of 
the  furnaces,  fitted  with  Adamson's  joints,  actually  tore  through 
the  bottom  of  the  flanging  the  first  time  steam  was  raised.  The 
only  way  to  strengthen  furnaces  from  such  strains  is  either  to 
prevent  the  difference  of  temperature,  or  else  to  allow  the  crown 
freedom  to  expand." 

To  prevent  the  differences  of  temperature,  although  it  is  un- 
doubtedly the  rational  way,  would,  however,  involve  either  a 
new  construction  of  boiler  or  a  different  method  of  firing,  and, 
consequently,  whilst  it  has  not  hitherto  been  often  attempted, 
many  efforts  have  been  made  to  provide  for  expansion  of  the 
furnace  tubes.  The  difficulty  here  has  been  that  these  tubes  are 
subject  at  the  same  time  to  the  steam  pressure,  tending  to 
collapse  them,  and  consequently  elasticity  longitudinally  could 
not  be  obtained  at  the  cost  of  strength  or  stiffness  circumferen- 
tially  or  radially.  Nevertheless,  the  corrugated  furnaces  of 
Holmes,  Fox,  Farnley,  Purvis,  and  Morison  (which  have  suc- 
cessively arisen  since  the  Bowling  and  Adamson  joints),  permit 
a  considerable  amount  of  expansion  to  take  place  without  bring- 
ing any  great  stress  on  the  furnace,  but  the  almost  incessant 
repetition  of  these  temperature  strains  under  ordinary  conditions 
of  stoking  has  caused  even  some  of  these  furnaces  in  time  to 


THE  MODERN  STEAM  BOILER.  25 

crack.  These  incessant  variations  of  temperature  depend  on  the 
conditions  of  the  fires,  the  opening  and  shutting  of  the  doors,  and 
the  cleaning  of  the  grates.  "  Those  variations  of  temperature," 
to  quote  Mr.  D.  P.  Morison,1  "  result  in  expansion  and  con- 
traction, producing  definite  mechanical  movements,  and  if  the 
design  of  the  furnace  is  such  that  it  cannot  readily  adapt  itself 
to  these  movements — and  no  plain  furnace  can — either  the 
material  becomes  distressed,  or  such  strains  are  produced  on 
the  boiler  that  leakage  results.  It  is  because  of  this  that 
excessive  corrosion  is  often  found  at  the  grate-bar  level  of  plain 
furnaces." 

In  the  case  of  the  boiler  shell,  there  is  not  the  same  frequency 
of  repetition  of  strains,  but  there  is  no  question  about  the  magni- 
tude of  the  stress  produced  on  the  plates  and  joints.3  In  con- 
sequence of  the  position  occupied  by  the  furnaces  in  the 
cylindrical  boiler,  the  water  under  the  level  of  the  fire  bars 
cannot  be  heated  by  ordinary  convection  currents  during  the 
process  of  getting  up  steam,  and  unless  some  special  means  are 
employed  to  lift  it  into  the  area  of  circulation  it  may  remain 
practically  cold  for  a  long  time.  Even  with  special  appliances 
some  hours  must  be  spent  in  gradually  raising  steam  in  order  to 
lessen  as  much  as  possible  the  difference  of  temperature  between 
the  top  and  the  bottom  of  the  shell.  The  tops  of  the  furnaces, 
stays,  and  tubes,  and  the  top  part  of  the  shell  are  soon  at  or 
above  the  temperature  of  the  steam,  whilst  below  the  furnaces 
the  shell  may  have  only  the  temperature  of  the  feed  water.  As 
in  the  case  of  the  furnaces,  the  top  portions  "  tend  to  expand 
more  than  the  bottom,  bringing  a  compressive  stress  on  the  top 
portions  of  the  boiler,  and  a  tensile  stress  on  the  bottom.  But 
as  the  sectional  area  of  the  upper  portion  exceeds  that  of  the 
lower,  so  do  the  tensile  stresses  exceed  in  intensity  the  com- 
pressive ones,  and  the  stress  is  so  severe  that  it  is  almost 
universal  to  find  the  ring  seams  at  the  bottom  of  the  boilers  to 
be  so  strained  as  to  be  leaky,  whilst  the  longitudinal  seams  are 
for  the  most  part  tight."  "  In  several  boilers  (mostly  double- 
ended  ones)  these  stresses  have  been  so  severe  as  to  actually 
fracture  the  plate  between  the  rivet  holes  in  the  ring  seams." 

1  "  On  Marine  Boiler  Furnaces,"  Trans.  N.E.  Coast  Inst.  of  Engineers  and 
Shipbuilders.     January,  1893. 

2  See  "  On  the  Design  and  Use  of  Boilers,"  Engineering,  Vol.  xxvi.,  p.  284. 


26  THE  PRACTICAL  PHYSICS  OF 

Force  exerted  by  Expansion  by  Heat. — It  is  a  matter  of  some 
importance  to  have  the  possible  extent  of  such  forces  clearly 
denned.  This  has  been  done  by  comparing  the  direct  effects 
of  heat  with  the  results  produced  by  dynamic  or  mechanical 
means,  as  ascertained  by  those  who  have  investigated  the 
elasticity  of  metals.  In  Mr.  D.  Kirkaldy's  "  Experimental 
Enquiry  into  the  Tensile  Strength  and  Other  Properties  of 
Wrought  Iron  and  Steel"  (Glasgow,  1863),  there  is  the  follow- 
ing :  "  Professor  Barlow  states  that  the  mean  extension  per  ton 
per  square  inch  in  seven  experiments  on  iron  bars  varied  from 
•0001082  to  '0000841,  the  gross  mean  being  '0000956.  The 
strain,  which  was  just  sufficient  to  balance  the  elasticity  of 
the  bar,  was  found  to  vary  from  n  to  8J  tons.  He  remarks  'We 
may  consider,  therefore,  that  the  elastic  power  of  good  medium 
iron  is  equal  to  about  ten  tons  per  inch,  and  that  this  force 
varies  from  ten  to  eight  tons  in  indifferent  and  bad  iron.  It 
appears  also  (considering  '000095  as  representing  in  round 
numbers  TO^^TT)  that  a  bar  of  iron  is  extended  one  ten-thousandth 
part  of  its  length  by  every  ton  of  direct  strain  per  square  inch 
of  section,  and  consequently  that  its  elasticity  will  be  fully  ex- 
cited when  stretched  to  the  amount  of  one  thousandth  part 
of  its  length/  " 

The  experiments  by  W.  H.  Barlow1  were  made  the  basis  of 
a  comparison  between  the  effects  of  heat  and  those  of  mechanical 
stress  by  Prof.  W.  Allen  Miller,2  who  found  that  by  raising  the 
temperature  ot  a  bar  of  wrought  iron  of  a  square  inch  (or  25*4 
mm.)  in  section  nine  degrees  Centigrade,  or  i6'8  degrees 
Fahrenheit,  the  same  elongation,  viz.,  TO-CITO  °f  its  length,  was 
produced  as  was  due  to  its  being  stretched  when  cold  by  a  ton 
weight.  A  range  of  temperature  of  only  45°  C.  (or  81°  F.)  will 
cause  a  similar  wrought  iron  bar,  ten  inches  (0*254  metre)  long, 
to  vary  in  length  five  one-thousandths  of  an  inch  (or  0-127  mm.), 
and  if  under  these  circumstances  the  two  extremities  of  the  bar 
were  securely  fixed,  so  that  elongation  could  not  take  place,  that 
increase  of  temperature  would  produce  a  stress  equal  to  about 
five  tons  per  square  inch. 

Calculating  upon  Joule's  data,  Prof.  Allen  Miller  remarked  that 
it  may  be  estimated  that  the  force  exerted  by  heat  in  producing 

1  Phil.  Trans.     1855.  2  "  Chemical  Physics."     4th  edition,  p.  261. 


THE  MODERN  STEAM  BOILER.  27 

the  expansion  of  one  pound  of  iron  between  o°  and  100°  C.  (32° 
and  212°  F.),  during  which  it  would  increase  about  ^^  of  its 
bulk,  would  be  adequate  to  lift  a  weight  of  seven  tons  to  the 
height  of  one  foot,  or,  in  other  words,  would  be  represented  by 
seven  foot-tons. 

Ordinary  wrought-iron  plates,  it  has  been  said,  when  left  free 
from  stress,  expand  about  -0000064  of  their  linear  dimensions  for 
each  degree  F.  increase  of  temperature,  and  assuming  this  to  be 
iron  of  ordinary  ductility,  of  which  the  modulus  of  elasticity, 
according  to  Prof.  Rankine  l  is  taken  at  29,000,000,  a  stress  of 
1  86  Ibs.  per  square  inch  would  produce  the  same  elongation  as 
one  degree  F.  So  that  where  a  plate  that  is  not  free  to  move 
is  subjected  to  elevation  of  temperature,  each  degree  Fahren- 
heit increase  of  temperature  subjects  it  to  a  compressive  stress 
of  1  86  Ibs.  per  square  inch,  and  each  degree  of  reduction  of 
temperature  to  a  tensile  stress  of  a  like  amount.  It  may  readily 
be  understood,  therefore,  that  serious  results  may  be  produced 
in  boilers,  portions  of  which  are  subjected  to  repeated  strains  of 
that  nature  by  fluctuations  of  temperature. 

Prof.  Thurston  (in  "  A  Manual  of  Steam  Boilers  ")  gives  the 
following  formulae  for  calculating  the  stress  produced  by  change 
of  temperature.  He  takes  as  the  modulus  of  elasticity  for  good 
wrought  iron  or  steel  E  =  28,  000,000  pounds  per  square  inch,  or 
2,000,000  kilogrammes  per  square  centimetre,  and  as  the  co- 
efficient of  expansion  X=o-ooooo68  for  Fahrenheit  degrees,  or 
0*0000120  for  Centigrade  degrees. 

Then  E=the  modulus  of  elasticity, 

X=the  change  of  length  per  degree  per  unit  of  length, 
A/°=the  difference  of  initial  and  final  temperature, 
p=the  stress  produced  :  — 

p:E:  :XA/°  :i 


and  with  above  values  for  E  and  \ 

^=190  A  /°  F.  nearly 

=  25A/°C.  „ 

For  cast-iron  taking  E  =  16,000,000,  and  X=  0^0000062 
p  =  iooAt°  F.  nearly 

=  I2A/°C.          „ 
1  "  A  Manual  of  Applied  Mechanics."     Second  edition,  p.  631. 


28 


THE  PRACTICAL  PHYSICS  OF 


Further  evidence  of  the 
destructive  effects  of  un- 
equal heating  in  boilers 
is  afforded  by  experiments 
made  on  this  subject  by 
Mr.  A.-F.  Yarrow  and  by 
Dr.  A.  C.  Kirk.  The  in- 
troduction of  the  higher 
temperatures  of  combus- 
tion which  are  clue  to  the 
employment  of  mechani- 
cally produced  draught, 
with  an  increased  pres- 
sure of  air  in  the  stoke- 
hold or  in  the  furnace, 
over  that  which  could 
be  obtained  by  chimney 
draught,  very  soon  was 
followed  by  serious  leak- 
ing in  parts  of  the  boilers, 
principally  at  the  tube 
ends  or  joints  in  the  tube 
plates. 

Mr.  Yarrow,1  finding 
that  some  boilers  of  the 
locomotive  or  "  Admi- 
ralty "  pattern  in  torpedo 
boats  gave  trouble  from 
tubes  leaking  on  trial, 
carried  out  some  interest- 
ing investigations.  The 
design  of  boilers  is  shown 
in  Figs,  ii  and  12.  "To 
ascertain  exactly  what 

1  "  Boiler  Construction,  Suit- 
able for  Withstanding  the 
Strains  of  Forced  Draught  so 
far  as  it  Affects  the  Leakage 
of  Boiler  Tubes,"  by  A.  F. 
Yarrow.  Trans.  Inst.  N.A. 
1891.  Vol.  xxxii.,  p.  98. 


THE  MODERN  STEAM  BOILER. 


29 


was  going  on  in  the  region  of  the  tube  plate,"  says  Mr.  Yarrow, 
"  we  removed  the  row  of  stays  nearest  to  the  tube  plate 
flange  on  the  sides  and  top  of  the  fire-box.  We  replaced  these 
stays  by  others  working  in  stuffing  boxes 
and  having  a  nut  on  the  outside,  so  that 
if  a  tensile  strain  had  to  be  met  they 
were  there  to  receive  it,  while  if  the 
inside  box  wanted  to  expand  it  had 
freedom  to  do  so.  See  Fig.  13.  This 
experiment  was  most  instructive.  Every 
time  the  fire  was  urged  these  stays 
would  all  move  outward  through  their 
stuffing  boxes,  owing  to  the  expansion 
of  the  fire-box.  In  some  cases  the  move- 
ment was  sufficient  to  enable  a  penny 
piece  to  be  inserted  between  the  nut 
on  the  stay  and  the  gland.  Each  time 
the  fire-door  was  opened  and  the  tem- 
perature reduced,  these  stays  would  move  inward,  and 
when  the  boiler  was  cool  the  nuts  pressed  hard  on  the 
glands.  From  the  moment  the  new  stays  were  fitted  the 
boiler  was  altogether  free  from  leaky  tubes.  ...  It  is,  of 
course,  dangerous  to  draw  a  conclusion  from  one  isolated 


FIG.    13. 


°ogogog6go° 
°gogogo° 
°o°o2oxo 


FIG.   14. 


experiment.  At  the  same  time  it  seems  more  than  probable 
that  these  stays,  as  originally  fitted,  had  much  to  do  with 
the  leaking  of  the  tubes,  because  it  is  evident  that  a  tensile 
strain  coming  on  a  tube-plate  weakened  by  being  perforated 


3o  THE  PRACTICAL  PHYSICS  OF 

with  a  number  of  holes  is  likely  to  distort  the  plates.  As  a 
matter  of  fact,  prior  to  the  new  stays  being  fitted,  this  tube 
plate  was  more  or  less  altered  in  shape  after  every  trial. 
Fig.  14  shows  exactly  the  change  that  took  place  on  the 
first  trial  alone.  It  will  be  seen  that  between  the  points  indi- 
cated on  the  diagram  there  was  in  one  case  an  extension  of  J  in., 
and  in  the  other  an  extension  of  f  in.  I  think  we  may  assume 
that  tube  plates  should  be  free  from  external  strains,  and  as  far 
as  possible  be  allowed  freedom  to  move  as  the  changes  of 
temperature  require." 


FIG.   15. 

To  observe  the  curvature  of  the  tubes  under  unequal  heating, 
during  the  process  of  raising  steam  and  afterwards,  Mr.  Yarrow 
arranged  the  apparatus  shown  diagrammatically  in  Fig  15. 
Through  three  of  the  tubes  which  were  at  different  levels 
were  fitted  bars,  fixed  centrally  in  the  tube  at  the  end  next 
the  fire  and  also  in  the  middle  of  the  tube.  "  The  object  of 
this  experiment  was  to  ascertain  if  the  tubes  remained  straight, 
and,  if  not,  to  register  the  extent  of  the  bending,  which  could  be 
made  apparent  by  the  alteration  in  the  position  of  the  extreme 
ends  of  the  rods.  Almost  immediately  after  lighting  up  it  was 
found  that  the  top  row  of  the  tubes  was  evidently  heated  in 
advance  of  the  rest.  The  hotter  water,  as  might  have  been 
expected,  was  near  the  surface,  the  cold  water  at  the  bottom 


THE  MODERN  STEAM  BOILER. 


31 


remained  undisturbed,  and  the  top  of  the  boiler  was  also  cold, 
owing  to  there  being  no  steam  to  heat  it.  The  water  near  the 
surface  being  raised  in  temperature,  those  tubes  which  passed 
through  it  strove  to  increase  in  length,  but  owing  to  the  tube 
plates  being  fixed  they  were  unable  to  do  so,  and  consequently 
there  was  a  considerable  bending  of  the  tubes.  This  was  made 
evident  by  the  movement  of  the  end  of  the  rod.  After  the  fire 
had  been  alight  about  ten  minutes  the  second  bar  began  to 
move  as  the  water  at  the  lower  level  rose  in  temperature.  In 
like  manner,  after  a  further  interval,  the  third  bar  moved,  and 
the  bars  all  continued  to  move  until  such  time  as  steam  began  to 
rise.  As  soon  as  10  or  15  Ibs.  were  registered  the  pressure  on  the 
tube  plates  began  apparently  to  make  itself  felt,  and  forced  them 
apart,  throwing  a  tension  on  the  tubes  which  straightened  them. 
From  thence  up  to  160  Ibs.  the  tubes  showed  practically  no 
curvature.  This  experiment  proves  how  necessary  it  is  to 
provide  ample  elasticity  in  the  tubes,  so  as  to  conform  to  the 
conditions  which  have  to  be  complied  with  in  raising  steam." 

As  evidence  of  the  strains  caused  by  unequal  expansion  in  the 
boiler  shell  when  lighting  up  and  raising  steam,  Mr.  Yarrow 
published  the  following  Table  and  illustrations  : — 

TABLE  III. 

EXPANSION  OF  COPPER  TUBES  &  OUTSIDE  SHELL  WHEN  RAISING  STEAM. 
LIT  UP  AT   10.20  A.M.,  4  INCHES  OVER   FlREHOX. 


Time 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Steam     

o 

0 

c 

o 

o-5 

20-40 

60-80 

100-120 

140-160 

ELONGATION  OF  BARREL  IN  M/M.  LENGTH  MEASURED  3-FT.  4$-ix.=  1,028  M/M. 


Boiler  Shell  at  Water  Level... 

'2 

•6 

•8 

9 

i  "4 

2'0 

2'5 

27 

2-8 

Top         

o 

o 

0 

•4 

r6 

2'O 

2'5 

2'5 

2-8 

Bottom  

•2 

'3 

'4 

•8 

r6 

1-6 

25 

2'5 

25 

ELONGATION  OF  TUBES  IN  M/M.    LENGTH  OF  TUBE  S-FT.  io-IN.  =  i,i68  M/M. 


Top  Tube          
Bottom  Tube  

i'5 
"7 

1-6 
'9 

1-6 

i'5 

1-6 
i  '4 

2'5 

2"0 

27 
2'5 

2-9 
2-9 

3'8 
3'6 

40 

3-6 

This  Table  shows  the  longitudinal  expansion  of   the  boiler 
barrel  at  different  parts,  and  at  varying  periods  during  steam 


THE  PRACTICAL  PHYSICS  OF 


raising,  and  Fig.  16  illustrates  by  diagram  the  changes  in  length 
of  another  example.  The  movement  of  the  inside  fire-box  of 
the  boiler  dealt  with  in  the  above  Table  is  shown  by  Fig.  17. 
These  examples  proclaim  that  the  distortion  of  form  in  some 
parts  is  greater  during  the  process  of  steam  raising  than  when 
steam  has  been  raised.  "  In  cooling  down  the  strains  are 
not  so  great  and  are  quite  different  in  character  from  those 
met  with  in  lighting  up.  One  main  principle  must  be  borne  in 
mind,  that  any  changes  of  temperature  should  take  place  as 


f  Boiler  extension,  ai  cfcfferait 
mtfttta  steam,,  tvutA.  JvettO"  cut,  workma  level,  . 


I" 


1 

^0J 


GO 


70 


2O  30  40  50 

Jtfinutca  a/ter  liahttnq  ta> 

FIG.   16. 

slowly  as  possible.     The  sudden  putting  out  of  the  fire  is  there- 
fore bad  and  may  cause  tubes  to  leak." 

"  Assuming  that  a  tube  is  well  expanded,  it  will  remain  tight 
in  the  plate  so  long  as  nothing  takes  place — such  as  a  sudden 
reduction  of  temperature — to  cause  the  tube  to  be  reduced  to  a 
greater  extent  than  the  collective  elasticity  of  the  tube  plate  and 
the  tube.  Now,  when  steaming  hard,  if  the  fire-door  be  opened 
and  a  blast  of  cold  air  admitted,  the  tubes  through  which  it 
passes,  being  thin,  will  feel  the  effect  and  contract  before  the 
thick  tube  plate.  The  tubes  will  remain  tight  only  so  long  as 
the  chilling  does  not  tend  to  reduce  the  diameter  of  the  ti>be 
beyond  the  collective  elasticity  of  the  tube  and  the  plate. 


THE  MODERN  STEAM  BOILER. 


33 


Should  this  elasticitynot  be 
sufficient  to  make  up  for  the 
change  of  form,  the  tube 
will  leak.  If  the  tube  plate 
be  thin,  so  that  the  rate  of 
contraction  approaches  that 
of  the  tube,  difficulty  from 
this  cause  will  be  reduced. 
Anything  that  can  be  done 
to  increase  the  range  of 


of  PbUf   2* 

'/» 


5PM 


SIOPM    (1 

^ 


<Mr«L_  i 


Heating   18 

1-TJ.    18. 


&KPX 
<6U»  Steam, 


S3SPM 
ISC  U>». Guam  A 

FIG.    17. 


ThuJtnejts  of  PLeU»  7/K 
of  7lU>e     '/» 


Healed,  *O  Tlrne* 
ftp  Alteration 


FIG.   19. 


elasticity  of  the  tube  and  the 
tube  plate,  allowing  thereby 
larger  differences  of  tempera- 
ture, is  clearly  desirable." 

In  order  to  test  the  effects 
of  heating  on  tube  and  tube 
plates  of  different  thicknesses, 
Mr.  Yarrow  had  portions  of 
plates  fitted  with  tubes,  as 
shown  in  Figs.  18  and  19, 


34 


THE  PRACTICAL  PHYSICS  OF 


surrounded  with  thin  sheet  steel  so  as  to  form  a  receptacle  for 
water,  and  heated  over  a  smith's  fire.  Where  the  tube  plate  dif- 
fered considerably  in  thickness  from  the  tube,  the  thinner  metal 
was  necessarily  heated  more  quickly,  and  its  expansion  due  to  the 
temperature  being  prevented  by  the  cooler  plate,  it  was  gradually 
crushed  and  deformed,  so  that  leakage  soon  commenced. 
With  a  more  uniform  thickness  in  both  such  a  result  was 
prevented. 

Mr.  A.  C.  Kirk1  carried  out  a  short  series  of  experiments  by 
means  of  similar  apparatus,  shown  in  Fig.  20,  with  the  addition 
of  fusible  plugs,  one  of  tin,  one  of  lead,  and  one  of  antimony, 
which  were  inserted  half  into  the  tube  and  half  into  the  tube 


„• 

OJ      MO 

I 

Q 

C      70C 

^^-^^ 

°-  too 

K^ 

\—     300 

^ 

\ 

®    400 

\ 

-  ; 

_® 

0      *>0 

\ 

w  *tf 

i. 

Jf 

n»                                 I 

^ 

nif 

cc*»- 

1 

J 

0 

plate.  The  experiments  were  commenced  with  the  tube 
plate  2|  in.  thick,  with  a  steel  tube  of  2\  in.  diameter  in- 
serted in  it  and  expanded  in  the  usual  way,  the  tube  plate 
being,  after  each  experiment,  reduced  in  thickness  by  having 
a  portion  turned  off  its  lower  surface.  Experiments,  con- 
tinuing each  for  half  an  hour  or  three-quarters  of  an  hour, 
were  made  with  the  tube  plate  thickness  successively  2|  in., 
ij  in.,  \\  in.,  if  in.,  a  mean  of  \\  in.  (i.e.,  not  truly  turned, 
having  been  left  j  in.  thick  at  one  side  and  J|  in.  at  the  other), 
f  in.,  and  finally  ^  in.  The  temperature  to  which  the  tube  plate 
was  raised  at  the  fire  surface  was  supposed  to  be  indicated  by 
the  melting  point  of  the  metal  plug  or  plugs  which  were  found  to 
have  been  fused  in  each  experiment.  This  method,  however, 


1  Engineering,  Vol.  liv.,  pp.  78,  333. 


THE  MODERN  STEAM  BOILER. 


35 


could  give  only  an  approximation  to  the  real  temperature,  as 
several  causes  of  error  are  possible  in  such  circumstances,  the 
surface  of  the  plugs  at  one  point  being  no  doubt  exposed  to  the 
direct  heat  of  the  fire,  and  therefore  not  necessarily  registering 
the  temperature  of  the  iron  plate  or  tube.  Accordingly  Mr. 
Kirk  graphically  represented  his  results  in  the  following  way, 
Fig.  21,  drawing  the  curve  as  a  mean  between  the  highest  and 
lowest  possible  temperatures  as  represented  by  the  melting 
plugs. 

The  base  line  represents  the  temperature  of  the  water  when 
boiling,  and  the  thicknesses  of  plates  at  each  experiment  are  set 
off  as  abscissas  on  the  base  line,  the  ordinates  from  these  points 


HORIZONTAL      SECTION        OF      FIREBOX 
I»T    CLASS    TORPEDO     BOAT 


representing  the  temperatures  of  the  plate  at  the  tube  end,  to 
the  scale  which  is  given.  The  results  of  these  tests  simply  con- 
firmed Mr.  Yarrow's  conclusions  as  to  the  effects  of  great 
diversity  between  the  thicknesses  of  tube  and  plate. 

Mr.  Yarrow  also  found  that  in  addition  to  liability  to  deforma- 
tion of  tube  ends  by  inequality  of  heating,  there  was  also  a 
tendency  in  the  thick  tube  plate  to  assume  a  curved  form,  and  in 
the  holes  through  which  the  tubes  passed  to  alter  in  form. 
Experiments  were  carried  out  with  indicating  apparatus,  and 
Fig.  22  shows  a  horizontal  section  through  the  tube  plate  of  a 
first-class  torpedo-boat  boiler,  with  a  dotted  line  representing 
the  curvature  corresponding  to  the  results  indicated  in  the 
experiments  where  the  plate  was  free  to  move.  But  as  the  plate 
is  not  free  to  move  in  a  boiler,  Mr.  Yarrow  recognised  that 


c  2 


36  THE  PRACTICAL  PHYSICS  OF 

molecular  strains  are  set  up  by  the  repeated  variations  of  tem- 
perature between  its  two  surfaces  which  must  permanently 
damage  the  plate.  "  When  we  consider/'  he  says,  "  that  every 
time  the  fire  door  is  opened  and  closed,  the  plate  wants  to 
change  its  form  and  cannot  do  so,  and  when  we  bear  in  mind 
that  the  fire  door  in  a  large  forced  draught  boiler  is  frequently 
opened  and  shut,  say  once  in  every  minute,  which  in  twenty-four 
hours  corresponds  to  1,440  times,  it  is  easy  to  understand  that 
the  varying  expansions  and  contractions  set  up  severe  molecular 
strains,  and  that  the  tube  plate  is  undergoing  very  harsh 
treatment." 

Evidence  bearing  on  this  subject  has  been  furnished  in  the 
experiments  recorded  by  Mr.  A.  J.  (now  Sir  John)  Durston.1  In 
order  to  ascertain  the  conditions  to  which  the  metal  of  boilers 
might  be  exposed  during  work,  the  following  methods  were 
adopted  : — 

i.  To  ascertain  the  temperature  of  the  hot  side  of  a  plate 
through  which  heat  is  passing  to  boiling  water,  a  circular  flanged 
dish,  10  in.  in  diameter  outside,  3  in.  deep,  and  made  of  J-in. 
plate,  had  attached  to  its  bottom  on  the  fire  side  eight  fusible 
plugs  or  buttons  of  different  compositions,  having  melting  points 
ranging  between  220°  F.  and  250°  F.  This  dish  was  half  filled 
with  water,  and  was  exposed  to  the  heat  of  a  Bunsen  gas  flame, 
having  a  temperature  of  about  1500°  F.,  over  which  it  was 
allowed  to  remain  until  the  water  had  been  for  some  time  boiling 
briskly.  On  examination  it  was  then  found  that  the  alloys, 
whose  melting  points  extended  to  240°  F.,  had  melted,  but  that 
one  which  would  fuse  at  243°  F.  was  only  slightly  softened,  and 
this  was  held  to  show  that  the  temperature  of  the  plate  at  the 
fire  side  was  about  240°  F.  A  layer  of  grease  was 

spread  to  a  thickness  of  about  5\  of  an  inch  over  the  inside 
surface  of  the  bottom,  and  the  heating  repeated  as  before.  The 
temperature  of  the  outer  surface  of  the  plate  was,  under  these 
circumstances,  shown  by  the  fusible  alloys  to  have  been  about 
330°  F.,  or  90°  F.  higher  than  before,  this  increase  of  temperature 
being  due  to  the  non-conducting  layer  of  grease. 

5.  With  a  similar  vessel  24  in.  in  diameter,  2.\  in.  deep,  and 
of  plate  \  in.  thick,  placed  over  a  forge  or  smithy  fire  and  with 

1  Trans.  Inst.  N.A.  (1893)  Vol.  xxxiv.,  p.  130. 


THE  MODERN  STEAM  BOILER. 


37 


a  constant  supply  of  water  maintained  during  ebullition,  the 
temperature  with  moderate  blast  was,  as  before,  240°  F.,  but  it 
increased  to  280°  F.  with  a  stronger  blast  urging  the  fire. 
This  experiment  was  repeated  with  varied  conditions  on  the 
water  side  as  follows  : — 

TABLE  IV. 


Temperature 
of  Hot  side  of 
Plate. 

Temperature 
of 
Fire. 

With  clean  fresh  water  as  above     ... 

280°  F. 

2200°  F. 

,,      5  per  cent.  American  distilled  oil  (paraffin 
scale  extracted)  added 

310°  F. 

2300°  F. 

,,      fresh  water  with  2.\  per  cent,  of  paraffin    ... 

330°  F. 

2100°  F. 

„             ,             „          „            „      methylated 
spir,it    . 

300°  F. 

2500°  F. 

„      grease  T\th  of  an  inch  spread  on  plate 

Above 
550°  F. 

2500°  F. 

2.  A  small  experimental  apparatus  was  constructed  to  ascer- 
tain the  temperature,  at  the  centre  of  its  thickness,  of  a  plate 
resembling  a  boiler  tube  plate  exposed  to  a  forced  blast  fire.  A 
flanged  |-in.  plate  was  fitted  with  short  lengths  of  steel  boiler 


.  2  S- 

- 

S~   ., 

-ZS  . 

ifi 

c 

^  \ 

/£-" 



-f 

FIG.   23. 


tube,  as  shown  in  Fig.  23,  the  centre  tube  being  larger  in  order 
to  facilitate  the  drilling  of  some  holes  ^  in.  diameter  radially  in 
the  centre  of  the  thickness  of  the  plate.  In  these  holes  were 
placed  square  pieces  of  fusible  alloys  and  the  tubes  were  fixed 
in  position  by  roller  tube  expanders  as  usual.  Water  was  then 


3g  THE  PRACTICAL  PHYSICS  OF 

put  in  nearly  to  the  depth  of  the  flange  and  the  apparatus  was 
heated  by  a  forge  tire,  the  blast  being  used  and  the  temperature 
of  the  fire  being  estimated  at  about  2000°  F.  The  experiment 
was  continued  for  about  half  an  hour,  fresh  water  being  supplied 


FIG.    24. 


to  replace  the  quantity  evaporated.  It  was  found  that  the 
alloys  whose  fusing  points  ran  up  to  290°  F.  had  melted,  but  the 
next  in  order,  which  had  a  melting  point  of  336°  F.,  was  still 


ooooocbooo-^o 

OO$OO(J)OOOOO 
OOOOO&OOOOO 

00000600000 

•&OOO0OOOO 
000$0-®-0 

JDOOOCL 

• — I — J 

FIG.   25. 


FIG.    26. 


solid.     The  temperature  of  the  plate  at  the  centre  was  therefore 
taken  to  have  been  at  between  290°  F.  and  336°  F. 

9.  Further  experiments  on  the  temperature  of  the  tube  plate 
were  made  in  an  experimental  boiler  shown  in  Figs.  24,  25  and  26. 


THE  MODERN  STEAM  BOILER. 


39 


In  the  holes  of  five  of  the  tubes,  numbered  10,  14,  28,  45  and 
59,  as  in  Fig.  25,  four  pieces  of  fusible  alloys,  f  in.  long,  were 
inserted  radially  in  the  centre  of  the  section  of  the  tube  plate,  as 
shown  to  an  enlarged  scale  in  Fig.  27. 


FIG.  27. 


For  the  first  experiment,  which  was  continued  for  two  hours 
the  boiler  had  a  closed  ashpit  with  forced  draught  delivered  into 
it,  and  the  following  were  the  conditions  of  the  experiment  :— 

TABLE  V. 


Mean. 

Maximum. 

Steam  pressure 

14.  -j 

I  «O 

Air  pressure  in  closed  ashpit 

'3* 

,     '5' 

Temperature    of   combustion    chamber   by   Le 
Chatelier  pyrometer 

2850°  F. 

3100°  F. 

Temperature  in  tubes  (middle  of  length)  ... 
Temperature  in  smoke  box 

I5500  F. 
1400°  F 

1800°  F. 
1600°  F 

Coal  used  per  hour 

1  88  Its 

„             .,      square  foot  of  grate 

30  Its. 

Water  evaporated  per  hour  ... 

1039  Its. 

,,             „             „            per   square  foot   of 
tube  and  tube  plate  surface          

4-62  Its. 

Maximum  temperature  of  steam 

366°  F. 

4° 


THE  PRACTICAL  PHYSICS  OF 


The  condition  of  the  fusible  alloys  at  the  end  of  the  experi- 
ment is  shown  in  the  following  Table,  from  which  Mr.  Durston 
concluded  that  the  temperature  of  the  plate  at  the  middle  of  its 
thickness  did  not  rise  to  540°  F.  but  at  some  of  the  tube  joints 
it  rose  to  53o°F.: — 

TABLE  VI. 


No.  of 
Tube. 

Melting  Point 
of  Alloy,  Fahr. 

Condition  after  Experiment. 

r 

435 

Fused  completely. 

59       J 

450 

„              „ 

460 

„              „ 

I 

470 

„              „ 

"1 

480 
490 
500 

5)                              J) 

Not  fused. 

I 

540 

»            » 

r 

510 

»                 M 

,0 

520 

Fused  at  end  next  tube. 

530 

»             it 

I 

540 

Not  fused. 

r 

550 

M                » 

28    1 

6l7 
680 

773 

t>                »» 
J)                 V 

r 

550 

>)                       5 

,  j 

617 
680 

J)                     )) 

i 

773 

,, 

10.  For  some  subsequent  experiments  the  boiler  was  enclosed 
in  an  air-tight  stokehold  and  the  draught  was  supplied  by  a  more 
powerful  engine  and  fan  in  order  to  obtain  a  higher  rate  of 
combustion.  In  addition  to  the  fusible  alloys  in  the  middle  of 
the  section  of  the  plate,  four  pieces,  each  /%  in.  in  length,  and 
T3^  in.  in  diameter,  were  fitted  into  the  face  of  the  plate  around 
each  of  the  numbered  tubes,  as  shown  in  Fig.  28.  These 
pieces  projected  ^  in.  beyond  the  face  of  the  plate,  and 


THE  MODERN  STEAM  BOILER. 


41 


FIG.   28. 


were  of  different  materials  in  four  different  trials.    The  following 
are  the  data  of  the  trials  : — 

TABLE  VII. 


Trials. 

ist. 

2nd. 

3rd. 

4th. 

Duration  of  trial        ...     hours. 

5 

5 

5 

3t 

Pressure  of  steam     Ibs. 

145 

142 

140 

144 

Air  pressure  in  stokehold    ins. 

»-•{ 

3  for  2  hrs. 
3^  for  next  3  hrs. 

h 

2-9 

Total  coal  used  during  trial  Ibs. 

2800 

3188 

2632 

not  accurately 
taken 

Total  water  evaporated  ...  Ibs. 

14125 

H775 

13148 

10276 

Coal  per  sq.  ft.  of  grate  per 
hour    Ibs. 

90 

102 

84-2 

Water  evaporated  per  sq. 
ft.  tube  and  tube  plate 
surface  per  hour       ...  Ibs. 

12  '64 

13-22 

1176 

n  -99 

Temperature    in    combus- 
tion chamber     F. 

2750 

2500 

3100 

3200 

Amount     of     mineral     oil 
used    Ibs 

Oil  used  in  percentage  of 
fuel  

•07 

•05 

42 


THE  PRACTICAL  PHYSICS  OF 


On  the  first  trial,  with  clean  feed  water,  16  of  the  pellets  on 
the  face  of  the  plate  were  made  with  melting  points  from  490° 
to  690°  F.  and  the  remaining  four  were  of  antimony  (melting 
point  1060°  F.)  All  were  melted  except  the  four  antimony. 

On  the  second  trial,  also  with  clean  feed  water,  the  pellets 
placed  in  the  face  of  the  plate  around  each  of  the  five  tubes 
were  one  of  antimony  (1060°),  two  of  zinc  (750°)  and  one  of 
an  alloy  melting  at  690°,  arranged  as  in  Fig.  29.  Of 
these  the  five  antimony  and  three  of  the  zinc  at  tubes  14,  45 

and  59  remained  intact, 


O 


^690' 

FIG.   29. 


*>6b  whilst  all  the  rest  melted. 

On  the  third  trial,  with 
pellets  arranged  as  in  the 
preceding  trial,  9  Ibs.  of  oil 
were  fed  into  the  boiler 
with  the  feed  water.  The 
five  antimony  and  one 
zinc  pellet  (at  tube  45) 
out  of  the  pellets  remained 
intact,  but  all  the  rest 
melted. 

On  the  fourth  trial,  the 
boiler  not  having  been 
cleaned  out  after  the  pre- 
ceding trial,  an  additional  5  Ibs.  of  oil  was  admitted  with 
the  feed  water.  During  this  trial  the  tubes  gave  out  when 
cleaning  fires  after  3!  hours  working.  Around  tubes  10,  14  and 
28  (the  hottest  part  of  the  plate)  all  the  zinc  and  alloys  melted ; 
the  antimony  partly  melted  in  Nos.  14  and  28,  but  remained 
intact  at  No.  10.  Around  tubes  45  and  59  the  antimony  and 
zinc  remained  intact.  This  showed  that  the  plate  was  pre- 
sumably about  the  temperature  of  1060°  F.,  at  all  events  during 
the  latter  part  of  the  trial,  when  it  is  supposed  the  tubes  gave 
out,  whereas  in  the  former  trial  they  remained  tight  up  to  and 
above  the  temperature  of  melting  zinc  (75o°F.). 

The  five  tubes  were  then  drawn,  in  order  to  examine  the 
fusible  plugs  let  into  the  plate  radially.  These  had  been 
arranged  as  in  Fig.  30. 

All  were  found  melted  except  the  zinc  at  tubes  14  and  28. 
At  tubes  14  and  28  the  temperature  at  the  face  of  plate  is  held 


THE  MODERN  STEAM  BOILER. 


43 


to  have  been  1060°  F,  and  at  the  middle  of  plate  between  680° 
and  75o°F. 

Commenting  on  these  experiments  Mr.  Zittenberg1  (of  Nagy- 
Kanizsa,  Hungary)  made  the  following  observations  as  to  the 
stress  at  the  tube  ends  :— 

"A  tube  internally  heated  and  externally  cooled,  under  an 
assumed  temperature  T  on  the  fire  side,  /  on  the  water  side,  and 
expanded  diametrically  according  to  a  temperature  0,  between 
/  and  T,  is  under  compression  on  the  fire  side,  conforming 
to  the  difference  T  — 0,  and  under  tension  on  the  water  side 
conforming  to  0  —  t.  For  every  degree  Centigrade,  steel  suffers 
a  stress  of  320  Ibs.  per  square  inch  and  copper  270  Ibs.  per 
square  inch.  Taking  the  difference  between  mean  and  firebox 
temperatures  proportionally  to  the  thickness  of  the  plates,  you 
would  find  according  to  the  10  experiments  33°  C.  difference 


between  mean  and  hottest  temperatures  of  tube,  compressing  it 
to  10,000  Ibs.  per  square  inch.  Experiment  No.  9  showed  that 
the  fusion  pellets  indicated  the  exterior  of  the  tube  plate  to  be 
between  252°  C.  and  257°  C.,  while  pellets  of  268°  C.  and  273°  C. 
melting  point  fused  only  at  the  end  near  the  tube.  This  indi- 
cates an  excess  of  the  temperature  of  the  tube  over  the  mean  of 
the  plate  of  at  least  15°  C.,  giving  at  least  5,000  Ibs.  per  square 
inch  further  compression.  If  you  consider  that  the  tube  is  also 
highly  compressed  by  the  act  of  expanding,  the  difference 
of  temperature  between  tube  and  outer  shell  of  the  tube  plate, 
which  can  expand  only  according  to  its  mean  temperature  and 
not  according  to  the  extreme,  you  will  agree  that  the  sum  of 
these  stresses  comes  near  the  elastic  limit  and  transcends  it  when 
the  material  softens  at  higher  temperatures  and  tends  to  localise 
the  effects  which,  otherwise,  are  partly  expended  on  the  body 
of  the  tube. 


1  See  Engineering,  Vol.  lv.,  p.  440. 


44  THE  PRACTICAL  PHYSICS  OF 

"  If  we  add  to  all  this  the  difference  of  expansion  and  elastic 
strength,  we  understand  why  tubes  of  copper  and  brass  do  not 
do  well  in  tube  plates  of  steel,  as  also  steel  tubes  in  the  copper- 
plates of  locomotive  boilers  where  hard  water  deposits  a  thick 
scale.  .  .  . 

"  The  same  holds  good  for  the  ingress  of  cold  air,  which  does 
very  little  harm  to  the  locomotive  tubes  in  the  Tyrol,  with  its 
extremely  soft  water,  but  produces  instantaneous  leaking  in  part 
of  Hungary,  with  its  very  hard  water." 

It  is  manifest  that  most  water-tube  boilers  are  not  subject  to 
the  strains  which  produce  distortion  of  tube  plates  of  consider- 
able extent,  and  that,  consequently,  they  are  not  so  liable  to 
suffer  from  leaking  at  the  joints.  No  doubt  a  great  stress  is 
thrown  upon  thin  tube  joints,  but  to  resist  pressure  these 
probably  have  an  ample  margin  of  safety.  Mr.  Yarrow  has 
stated  that  a  2-inch  steel  tube  expanded  by  a  roller  expander  in 
a  steel  tube  plate  has  a  holding  power  of  8  to  12  tons  against 
stress.  In  the  firebox  of  a  boiler  of  locomotive  pattern,  with 
200  Ibs.  pressure  of  steam  per  square  inch  in  the  boiler,  the 
total  strain  tending  to  separate  the  two  tube  plates  is  equal  to 
124  tons,  whilst  the  total  holding  power  of  the  tubes  at  8  tons 
per  tube  was  found  to  be  2,300  tons,  giving  a  margin  of  safety  of 
nearly  20.  The  tubes  of  water-tube  boilers  have  the  advantage 
of  the  steam  pressure  being  within  them,  as  this  tends  to 
strengthen  their  hold  on  the  plates  or  chambers  into  which  they 
are  expanded  and  to  prevent  leaking  at  their  joints. 

It  must  not  be  supposed,  however,  that  water-tube  boilers 
are  wholly  exempt  from  oscillatory  strains,  or  that,  if  not  well 
designed  and  worked  with  regard  to  them  and  to  the  other 
actions  proceeding  during  the  use  of  such  boilers,  they  will  not 
suffer  also.  Their  larger  margin  of  strength  will,  no  doubt, 
cause  them  to  suffer  less  in  some  ways,  but  their  thinner 
material  will  sooner  cause  any  destructive  action  to  become 
apparent.  The  observations  and  remarks  on  the  action  of 
the  boilers  of  the  T.S.S.  "  Kherson,"  published  by  Mr.  G. 
Gretchin,1  Engineering  Superintendent  of  the  Russian  Volunteer 
Fleet,  furnish  us  with  some  useful  information  on  this  point. 
A  full  description  of  the  machinery  of  this  vessel  was  published 

1  Trans.  Inst.  Engineers  and  Shipbuilders  in  Scotland.  Vol.  xli.,  page  299. 
(1898). 


THE  MODERN  STEAM  BOILER.  45 

in  Engineering  of  6th  December,  1896,  n;id  a  graphic  log  of  part 
of  her  run  from  St.  Petersburg  to  Vladivostock,  and  from 
Vladivostock  to  Odessa,  is  printed  in  the  "  Transactions  of  the 
Institution  of  Engineers  and  Shipbuilders  in  Scotland."  (Vol.  xli.) 

There  are  in  this  vessel  24  Belleville  boilers,  placed  back  to 
back  athwartship,  in  three  separate  groups  of  eight  boilers  each. 
The  boilers  have  each  eight  elements,  consisting  of  20  lap- 
welded  iron  tubes  of  4^  in.  outside  diameter,  the  two  lower 
tubes  of  each  element  being  %  in.  thick,  the  two  next  fa  in. 
thick,  and  the  rest  J  in.  thick.  The  connecting  boxes  are  of 
cast  steel.  The  total  amount  of  heating  surface  is  35,350  square 
feet,  and  the  grate  surface  1,132  square  feet. 

On  the  occasion  of  the  first  mooring  trials  in  February,  1896, 
the  middle  group  of  boilers  was  under  steam,  the  conditions  of 
working  being  identical  for  the  boilers  on  the  starboard  side  and 
those  on  the  port  side,  except  that  it  was  found  at  the  end  of 
the  trial  that  the  ship  had  a  list  to  starboard  of  io|  degrees. 
The  boilers  on  the  starboard  side  worked  well,  but  leakage  took 
place  in  the  joints  of  the  bottom  boxes  with  the  feed  collectors 
in  all  the  port  boilers,  and  after  the  trial  it  was  found  that  nearly 
all  the  tubes  of  these  boilers  were  bent  downwards,  13  of  them 
being  out  of  line  from  i  in.  to  i^  in.  On  the  next  trial  the  list 
was  five  degrees  to  the  other  side,  and  a  similar  result  followed, 
to  a  less  degree,  in  the  tubes  of  the  starboard  boilers.  "  This 
coincidence  of  the  list  of  the  ship  and  the  irregularity  of  working 
of  the  boilers  on  one  side  was  observed  afterwards,"  Mr. 
Gretchin  remarks,  "during  the  whole  round  voyage."  Each 
time  there  was  a  list  leakage  was  found  in  the  feed  collector 
orifices  on  the  side  opposite,  and  the  feed  pumps  on  that  side 
also  worked  irregularly.  "  The  examination  of  the  tubes,  which 
was  made  each  time  the  boilers  were  stopped,  showed  the  bend 
of  the  tubes  to  be  downwards  on  the  opposite  side  from  that  to 
which  the  ship  was  listed,  and  what  was  of  greater  interest, 
the  tubes  on  the  other  side,  which  were  bent  before,  had  a 
tendency  to  become  straight,  and  some  of  them  even  got  bent 
upwards.  As  a  rule,  the  lower  tubes  of  Belleville  boilers  tend 
to  bend  upwards  if  the  boilers  are  working  in  their  normal 
condition." 

Mr.  Gretchin  had  previously  observed  this  latter  phenomenon 
in  the  boilers  of  the  French  steamer,  "  Ville  de  la  Ciotat,"  on 


46 


THE  PRACTICAL  PHYSICS  OF 


a  voyage  from  Marseilles  to  Port  Said.  He  explains  the 
correspondence  of  the  bending  of  the  tubes  and  the  list  of  the 
ship  as  follows :  "  Supposing  the  list  is  on  the  starboard  side, 
the  first,  third,  and  all  the  uneven  tubes  of  the  elements  of  the 
port  boilers  will  be  horizontal  if  the  list  is  equal  to  2\  degrees  ; 
and  the  back  ends  of  these  tubes  will  be  higher  than  the  front 
ends  when  the  list  is  greater  than  that."  This  is  illustrated  in 
Fig.  31,  showing  the  normal  position  of  the  tubes,  and  Fig.  32 
that  due  to  a  list  greater  than  2\  degrees.  "  In  this  case 
the  steam  generated  in  the  first  lowest  tube,  which  is  directly 
connected  with  the  feed  collector,  will  go,  or  have  a  ten- 
dency to  go,  to  the  feed  collector.  It  is  possible  that  under 
certain  conditions  the  power  of  motion  of  the  steam  bubbles  in 
this  direction  is  greater  than  the  force  which  produces  circulation. 


FIG.   32. 


At  the  moment  this  comes  into  action  the  water  supply 
will  be  checked,  the  tube  overheated  and  liable  to  be  bent 
downwards.  ...  If  this  return  motion  of  the  bubbles  takes 
place,  and  if  the  tubes  get  bent,  as  experience  proves,  it  is  quite 
possible  that  these  two  phenomena  may  occur  at  the  same 
moment.  When  the  tube  is  bending,  the  female  cone  of  the 
bottom  connecting-box  moves  on  the  male  cone  of  the  feed- 
collector,  and  the  result  is  leakage  through  the  joint.  This  sup- 
position is  proved  by  the  fact  that  the  leakage  was  always  much 
worse  in  the  boilers  which  were  working  under  conditions  un- 
favourable as  regards  circulation  of  water." 

After  a  voyage  from  Newcastle  to  St.  Petersburg,  the  tubes 
were  examined  outside  and  measured.  The  results  of  measure- 
ment of  the  two  lowest  tubes,  which  were  nearest  the  fire,  are 
given  in  the  following  Table,  in  which  the  top  row  of  figures 


THE  MODERN  STEAM  BOILER. 


47 


refers  to  the  different  elements  of  each  boiler,  and  the  first 
column  of  figures  denotes  the  individual  boilers  whose  tubes  are 
thus  dealt  with.  The  measurements  of  the  same  tubes  as  taken 
at  Newcastle  before  the  voyage  are  inserted  in  each  case  for 
comparison.  The  figures  without  arrows  represent  the  extent  of 
downward  bending,  and  those  with  arrows  indicate  upward 
bending. 

TABLE  VIII. 


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48  THE  PRACTICAL  PHYSICS  OF 

"  It  can  be  seen  from  the  Table  that  nearly  all  the  tubes  of  the 
port  boilers  were  bent  downwards,  and  three  of  them  as  much 
as  |  in.  In  the  second  row  of  tubes,  which  was  at  a  greater 
inclination  when  the  list  was  to  the  starboard  side,  the  bends 
decreased,  and  many  of  the  tubes  returned  to  their  original 
form.  The  change  of  form  of  the  tubes  on  the  starboard  side 
was  not  so  considerable  as  on  the  port  side  ;  nevertheless  in  23 
out  of  32  tubes  the  bend  had  decreased.  Six  of  these  23 
became  quite  straight,  and  four  tubes  even  got  bent  upwards. 

"  About  three-quarters  of  the  whole  number  of  tubes  were 
out  of  their  original  straight  form  when  the  '  Kherson  '  returned 
home.  ...  In  some  cases  the  tubes  were  bent  upwards,  but 
on  every  occasion  the  bend  was  in  accordance  with  the  list 
of  the  ship  when  the  boilers  were  under  steam.  The  largest 
number  of  tubes  were  bent  about  f  in.  in  the  middle,  the 
smaller  number  only  J  in.,  but  a  few  as  much  as  ij-  in." 

There  is  no  doubt  that  the  special  design  of  the  Belleville 
boilers — that  of  a  flattened  spiral — renders  it  specially  liable  to 
differences  of  temperature  in  the  tubes.  All  the  steam 
formed  in  each  tube  has  to  be  conveyed  by  that  tube,  which  is 
more  or  less  inclined  to  the  horizontal,  so  that  the  steam  must 
pass  along  the  upper  side  of  the  tube.  This  leaves  a  steam 
space  in  contact  with  the  top  side  of  the  tubes  of  all  boilers  con- 
structed with  nearly  horizontal  tubes,  and  as  the  under  sides  of 
the  same  tubes  are  in  contact  with  water,  there  may  be  a  con- 
siderable difference  in  temperature  between  the  two  sides.  In 
the  Belleville  boiler,  however,  this  result  is  increased  propor- 
tionately in  the  tubes  above  the  lowest  row,  because  each 
horizontal  tube  in  the  spiral  has  to  convey,  not  only  its  own 
steam,  but  also  all  that  is  formed  in  the  tubes  below  it.  In  the 
topmost  rows,  before  the  steam  chamber  or  drum  is  reached,  as 
a  consequence,  there  may  be  nothing  but  steam,  or  only  a  little 
water  broken  up  into  froth,  and  these  tubes  may  readily  attain 
a  temperature  considerably  higher  than  those  of  the  lowest  rows, 
where  there  must  be  a  considerable  quantity  of  water  present 
while  the  boiler  is  at  work.  All  these  opportunities  for 
differences  of  temperature  point  to  possible  strains  which  had 
much  better  be  avoided. 

"  Every  design/'  remarked  Mr.  Yarrow  at  the  close  of  his 
paper,  "  is  more  or  less  a  compromise,  but  the  investigation 


THE  MODERN  STEAM  BOILER.  49 

which  we  have  made  points  to  the  importance  of  leaving 
nothing  undone  to  ensure  a  design  conforming  to  the  require- 
ments of  changes  of  form  due  to  changes  of  temperature.  It 
also  points  to  the  importance  of  adopting  only  the  highest 
classes  of  material,  so  as  to  ensure  ample  elasticity  to  help  in 
conforming  to  these  changes,  some  of  which  are  considerable." 
After  such  an  object-lesson,  it  is  clear  that  we  can  with  con- 
fidence formulate  certain  axiomatic  statements  of  the  require- 
ments of  boiler  design. 

1.  Strength  should  be  the   maximum  for  the  pressure,  and 
should  be  due  to  form,  not  to  thickness  of  material,  or  artificial 
strengthening  by  stays. 

2.  Weight  should  be  the  minimum  per  unit  of  power,  con- 
sistent with  strength.      This  is  true,  not  only  for  marine  boilers, 
because  useless  weight  means  useless  material  and  unnecessary 
strains  upon  structure  and  supports. 

3.  The  design  should  provide  for  facility  of  construction  and 
repair. 

4.  The  form  must  be  regulated  by  the  requirements  of  the 
circulation  of  the  water  and  of  the  heating  medium. 

5.  The  heating  surface  should  be  the  maximum  consistent 
with  other  requirements. 

The  first  three  of  these  really  follow  from  what  has  been 
before  us  in  this  chapter  ;'  the  evidence  for  the  last  two  we 
have  still  to  consider,  although  the  "  Kherson's  "  boilers  afford 
some  illustration  of  No.  4. 


CHAPTER  III. 
COMBUSTION. 

COMBUSTION  is  necessarily  the  first  action  which  takes  place  in 
the  process  of  steam  generation,  and  in  this  process  the  problem 
which  is  presented  to  us  is  a  two-fold  one,  viz.  :  First,  how  to 
obtain  the  maximum  amount  of  heat  from  the  fuel  which  is 
employed,  and  second,  how  to  transmit  the  maximum  amount  of 
that  heat  to  the  water.  The  first  portion  of  this  problem  is  what 
concerns  us  here,  and  the  first  step  in  it  is  to  ascertain  what  is 
the  maximum  amount  of  heat  derivable  from  the  fuel.  The 
main  facts  of  the  chemistry  of  combustion  have  been  repeatedly 
set  forth  in  text  books,  and  to-day  may  be  said  to  form  a  portion 
of  the  alphabet  of  engineering  knowledge.  Yet  we  find  in  this, 
as  in  other  departments  of  our  subject,  that  there  is  abundant  room 
for  further  research  and  improvement,  or  advance  in  knowledge. 

Calorific  Value  of  Fuel. — The  ultimate  constitution  of  fuels,  or 
the  proportions  of  the  various  elementary  bodies  into  which 
they  are  resolved  by  the  processes  which  are  employed  therein, 
can  be  learned  from  ordinary  chemical  analysis.  In  statements 
of  analysis  of  coal,  we  have  usually  given  to  us  the  percentage 
proportions  of  carbon  and  hydrogen  into  which  the  coal  has  been 
resolved  by  the  action  of  heat,  and  these  are  used  in  calculations 
of  the  calorific  power  of  the  fuel  as  represented  by  the  units  of 
heat  yielded  by  the  combination  of  these  elements  with  oxygen. 

But  the  sum  of  the  substances  into  which  coal  or  other  fuel 
can  be  resolved  by  the  heat  or  other  actions  employed  in  a 
chemical  analysis,  tells  us  very  little  about  the  proximate  com- 
position of  the  fuel  analysed.  And,  speaking  generally,  the 
temperature  to  which  the  small  sample  of  say,  coal,  is  subjected 
during  the  course  of  an  analysis  may  produce  effects  \vhich 
are  somewhat  divergent  from  those  which  are  produced  when 
the  same  coal  is  subjected  to  very  different  conditions  in  actual 
use.  Coal  does  not  consist  of  carbon  merely  mixed  writh 
hydrogen,  but  is  composed  for  the  most  part  of  solid  hydro- 
carbons, the  formation  of  which  from  woody  fibre  by  successive 

50 


THE  MODERN  STEAM  BOILER. 


dehydrations  is  well  understood  by  chemists,  who  have  termed 
this  process  "  cumulative  resolution."  '  Very  little  has,  however, 
been  done  towards  separating  these  various  hydrocarbons  in 
their  natural  state  from  coal,  and  showing  in  what  manner  they 
are  grouped  or  held  together  in  that  substance.  A  very  excellent 
commencement  of  such  investigations  is,  however,  described  in 
44  A  Contribution  to  the  Chemistry  of  Coal,  etc.,"  by  W.  Carrick 
Anderson,  M.A.,  B.Sc.,  Assistant  to  the  Professor  of  Chemistry, 
Glasgow  University.  (See  Proc.  of  the  Philosophical  Society  of 
Glasgow,  Vol.  xxix.,  pp.  72-96.)  From  this  research,  it  seems 
to  be  probable  that  the  different  varieties  in  the  quality  and 
composition  of  coal  (such  as  anthracite,  gas  coal,  splint  coal, 
coking  coal,  soft  coal,  etc.),  are  due  to  degrees  of  oxidation  of 
the  coaly  matter  when  "  resolved  "  from  woody  fibre.  When 
heat  is  applied  to  coal,  gaseous  hydrocarbons  of  varying  com- 
position are  formed  by  reactions  taking  place  in  the  substance  of 
the  coal  itself,  and  are  evolved  from  it  ;  a  certain  quantity  of 
what  is  called  "  fixed  carbon  "  or  "  coke,"  but  which  should  be 
called  "  deposited  carbon,"2  remaining  after  all  the  gaseous 
hydrocarbons  have  been  driven  off. 

The  following  Table  exhibits  the  differences  between  the 
calorific  powers  and  specific  heats  of  five  known  varieties  of  pure 
solid  carbon,  as  found  by  Favre  and  Silbermann,3  who  deduced 
from  them  the  conclusion  that  there  is  no  exact  relation  between 
the  calorific  power  and  the  specific  heat  of  carbon  in  the 
different  allotropic  states. 

TABLE  IX. 


Variety  of  pure  Carbon. 

Calorific  Power. 

Specific  Heat 
(Kegnault). 

\Voocl  charcoal 

8080 

0*24150 

Gas  retort  carbon 

8047-3 

0-20360 

Artificial  graphite 

7762-3 

O-197O2 

Native  graphite 

77(/r6 

0-20I87 

Diamond 

7770-1 

0-14687 

1  On  "  Cumulative  Resolution,"  by  Prof.  E.  J.  Mills,  D.Sc.,  F.R.S. 
-  See  "  On  Fuel  and  its  Applications,"  by  E.  J.  Mills,  D.Sc.,  and  F.  J.  Rowan. 
Vol.  i.  of  Groves  and  Thorp's  Chemical  Technology.     London,  1889. 
:i  Sec  Percy's  "  Metallurgy,"  Fuel,  p.  163. 


52  THE  PRACTICAL  PHYSICS  OF 

These  facts  have  also  suggested  the  conclusion  that  the  heat 
of  combustion  of  an  elementary  substance  depends  not  only 
upon  its  chemical  constitution,  but  also  upon  its  physical  state 
before  combustion.1  Favre  and  Silbermann  also  noticed  that 
the  density  of  both  simple  and  compound  bodies  exerts  an 
influence  upon  their  calorific  value,  and  that  the  fuel  value  of 
polymeric  bodies  varies  with  the  state  of  condensation  of  their 
molecules,  with  which  it  is  in  inverse  ratio.  As  an  illustration  of 
the  differences  existing  in  simple  bodies  in  different  allotropic 
conditions,  they  instanced  carbon  vapour,  whose  fuel  value  they 
reckoned  at  11,214  calories,  natural  graphite  they  valued  at 
7796-6,  and  diamond  at  7770  calories. 

The  fuel  value  of  the  "  fixed  carbon,"  "  coke,"  or  "  deposited 
carbon,"  into  which  a  portion  of  coal  is  resolved  depends,  there- 
fore, upon  its  density,  which  is  largely  determined  by  the 
temperature  and  pressure  at  which  its  formation  has  taken 
place. 

With  regard,  also,  to  the  hydrocarbons  which  are  formed  by 
the  action  of  heat  on  coal,  their  composition  depends  upon  the 
temperature  to  which  the  coal  has  been  exposed  during  distilla- 
tion or  decomposition,  and  since  the  calorific  value  of  the 
different  hydrocarbons  varies  with  their  constitution  and  that  of 
solid  carbon  with  its  physical  state,  it  is  evidently  not  easy  to 
find  an  exact  relation  between  the  results  yielded  by  any  given 
coal  on  analysis  and  those  found  in  actual  use.  Even  with 
different  methods  of  use  different  results  are  obtained.  In  con- 
nection with  this  subject,  another  consideration  deserves  some 
attention.  In  the  calculation  of  the  calorific  value  of  fuels,  it  is 
always  assumed  that  all  the  carbon  of  the  fuel  exists  in  it  as  solid 
carbon  and  has  the  value  of  wood  charcoal  burning  to  carbon 
dioxide,  whilst  all  estimations  of  the  calorific  power  of  hydrogen 
are  made  with  it  in  the  state  of  gas.  In  neither  case  does  this 
truly  represent  the  actual  condition  of  the  fuel. 

In  the  case  of  coal,  a  considerable  portion  of  the  carbon  must 
burn  in  the  state  of  gas  along  with  the  hydrogen,  both  elements 
having  been  previously  united  in  a  solid  form.  In  the  case  of 
liquid  fuel,  none  of  the  carbon  or  hydrogen  exists  in  a  solid  form, 


1  See   "  Coal,  its    History   and  Uses,"  by  Prof.   Rucker,    p.   243.     London 
Macmillan,  1878. 


THE  MODERN  STEAM  BOILER.  53 

and  both  substances  must  be  wholly  consumed  in  the  state  of 
gas,  if  that  kind  of  fuel  is  to  be  economically  used. 

An  illustration  of  the  nature  of  the  discrepancies  which  may, 
and  undoubtedly  often  do,  exist  between  the  heat  values,  as 
calculated  from  elementary  composition  and  as  found  in  actual 
use,  is  afforded  by  a  comparison  of  marsh  gas  with  acetylene. 
Marsh  gas  is  represented  by  CH4,  but  it  has  been  found  that 
1 6  grams  of  marsh  gas  give  out  in  burning  less  heat  than  do 
the  12  grams  of  carbon  and  4  grams  of  hydrogen  gas  of  which 
it  is  composed.  It  is  readily  decomposed  by  heat  into  its 
elements",  and  is  generally  formed  by  actions  taking  place  at  a 
low  temperature.  Acetylene  (C2H2),  on  the  other  hand,  has  a 
higher  heat  value  than  is  shown  by  the  sum  of  its  elements,  as 
26  grams  of  C2H2  give  more  heat  than  do  24  grams  of  carbon 
and  2  grams  of  hydrogen  gas.  Unlike  marsh  gas,  acetylene 
is  produced  by  reactions  taking  place  at  a  high  tempera- 
ture, and  this  may  account  for  its  greater  potential  energy. 
One  of  the  fundamental  principles  of  thermo-chemistry  is  that 
the  quantity  of  heat  evolved  is  the  measure  of  the  sum  of  the 
chemical  and  physical  work  accomplished  in  the  reaction.  This, 
of  course,  supposes  that  all  the  actions  taking  place  in  the 
accomplishment  of  a  given  result  are  known,  so  that  the  elements 
of  which  that  result  is  composed  can  be  counted.  When,  for 
instance,  solid  bodies  become  by  chemical  union  a  gaseous  com- 
pound, heat  is  absorbed  or  becomes  latent,1  and  a  portion  of  this 
heat  may  become  sensible  during  the  transfer  of  one  of  these 
gaseous  constituents  to  another  combination.  With  regard  to 
coal,  however,  it  cannot  be  pretended  that  we  know  all  the 
reactions  taking  place  during  its  combustion,  or  the  full  effect  of 
conducting  that  combustion  at  various  temperatures.  In  general, 
the  theoretical  thermic  values  of  the  different  elements  calculated 
as  burned  in  oxygen  are  taken  as  the  basis  of  calculation  of  the 
heat  value  of  fuels,  with  some  small  deductions  due  to  the 
presence  of  oxygen  in  the  fuel,  to  the  employment  of  atmospheric 
air,  and  to  the  specific  heat  of  the  products  of  combustion. 

The  following  Table  shows  these  theoretical  calorific  values  of 
the  principal  substances  found  in  coal  and  other  fuel. 


1  See   "  On  the  Physical  Conditions  Existing   in  Shale-distilling  Retorts," 
by  F.  J.  Rowan,  Jour.  Soc.  Chem.  Industry,  Vol.  x.,  1891. 


54 


THE  PRACTICAL  PHYSICS  OF 
TABLE  X. 


Hydrogen  burned  in  oxygen  ... 

Symbol  and  atomic  weight. 

Heat  evolved  by  the  com- 
bustion of  i  Ib.  of  substance. 

Before 
combustion. 

After 

combustion. 

British 
thermal  units 
(Ib.F.  degrees) 

Ibs.  of  water 
evaporated 
from  and  at 

212°. 

H            i 

H,O     18 

62,032 

64-2I 

Carbon  burned  in  oxygen  to  CO 

C              12 

CO       28 

4,451 

4'6l 

Carbon  burned  in  oxygen  to  CO2 

C              12 

C02     44 

14,544 

I5-06 

Carbonic   .oxide     burned     in 
oxygen  CO2 

CO      28 

C()2     44 

4,326 

4-48 

Olenant  gas  (ethylene) 

C2H4   28  { 

2H°6}12-* 

21,343 

22-09 

Marsh  gas  (methane) 

CH4     16  1 

$b}*> 

23,513 

,«4 

With  regard  to  the  oxygen  in  the  fuel,  as  it  exists  for  the  most 
part  in  moisture,  hygroscopic  or  free,  and  is  therefore  useless  for 
combustion,  being  already  combined  with  its  equivalent  of 
hydrogen,  it  is  usual  to  deduct  from  the  hydrogen  one- eighth  of 
the  weight  of  the  oxygen.  The  remainder  of  the  hydrogen  is 
called  the  "  disposable  hydrogen,"  and  in  calculations  of  calorific 
power  is  generally  reduced  to  the  heat-producing  equivalent  of 
carbon.  The  general  statement  of  the  calculation  for  calorific 
value  is  therefore  : — 

Calorific  value  =  14,544 JC  +  4-265  (li—  -\ } 

For  the  quantity  of  water  which  the  fuel  can  evaporate  from 
and  at  212°  Faht.  (966  British  heat  units  being  required  per  Ib. 
of  water  evaporated),  the  following  is  used  : — 

Ibs.  of  water  evaporated  =  15*06 JC  +  4-265  (H—  —  J  j 

In  some  books  the  round  numbers  62,000  for  hydrogen,  and 
14,500  for  carbon,  are  adopted  in  calculating  heat  values  of  fuel, 
and  this  causes  a  slight  alteration  in  the  figures  given  above. 

Thus  D.  K.  Clark1  gives  the  following  formula  for  heating 
power  : — 

A=i4S  (C  4-  4-28  H) 


1  "  The  Steam  Engine,"  Vol.  i.,  p.  38. 


THE  MODERN  STEAM  BOILER.  55 

and  for  evaporative  power  :  — 

(with  water  supplied  at  62°)  £=0-13  (C  +  4*28  H) 
(with  water  supplied  at  212?)  e=o'i$  (C  +  4*28  H) 

These  calculations  afford  approximate  estimates  (apart  from 
the  effects  of  the  products  of  combustion)  of  the  value  of  fuels 
for  steam  raising,  but  it  is  well  known  that  they  are  certain  to 
give  results  which  are  short  of  what  can  be  realised  with  fuel 
properly  used. 

Efforts  have  not  been  wanting  to  improve  the  basis  of  such 
calculations,  so  that  their  result  should  come  nearer  to  the 
possible  with  fuel  in  actual  use.  One  of  the  best  attempts 
hitherto  was  made  by  M.  Cornut,1  chief  engineer  to  the  Northern 
(of  France)  Steam  Users'  Association,  who  suggested  the  formula 
(expressed  in  calories)  :— 


when  Q=the  total  quantity  of  heat, 

C=the  fixed  or  solid  carbon,  and 

C!=the  volatile  carbon  contained  in  the  coal. 

The  uncertain  factor  in  this  case,  however,  is  the  value 
ascribed  to  the  gaseous  carbon,  because,  as  we  have  seen,  all 
hydrocarbons  have  not  the  same  calorific  value,  which  depends, 
no  doubt,  to  a  great  extent  on  the  temperature  of  their 
forniation. 

In  the  case  of  liquid  fuel,  Harrison  Aydoir  proposed  to  give 
all  the  carbon  contained  in  it  the  heat  value  of  21,600  British 
heat  units  (that  is,  practically  the  same  value  as  M.  Cornut 
employed  in  calories),  which  Prof.  Rankine  had  stated  was  the 
number  due  to  gaseous  carbon.  A  small  expenditure  of  heat, 
however,  suffices  to  gasify  the  whole  of  the  oil  of  most  qualities 
which  are  used  for  fuel,  and  when  this  preliminary  gasification 
is  properly  carried  out  the  resulting  gas  has  usually  a  much 
higher  calorific  powrer  than  is  represented  by  the  constituents  of 
the  oil  itself3  as  analysed.  It  seems  to  be  quite  possible  to 
improve  the  methods  of  analysing  fuels,  with  a  view  to  the  report 

1  "  Etudes  sur  la  Combustion  cle  la  Houille,"  from  Bulletin  de  la  Societe 
Industrielle  de  Mulhouse.  Paris,  1^75. 

-  Min.  Proc.  Inst.  C.E.,  Vol.  Hi. 

3  See  "  On  the  Calorific  Value  of  Solid  and  Liquid  Fuels,"  by  F.  J.  Rowan, 
Jour.  Soc.  Chem.  Industry,  Vol.  vii.,  p.  195. 


56  THE  PRACTICAL  PHYSICS  OF 

of  analysis  giving  a  better  conception  of  their  calorific  value,  and 
the  author  of  this  work  has  suggested  (in  "  Fuel  and  its  Applica- 
tions," page  709)  a  direction  which  such  methods  might  usefully 
take. 

Illustration  of  the  insufficiency  of  present  methods  is  afforded 
by  the  results  of  the  elaborate  trials  of  fuel  in  quantity  for  steam 
raising  which  were  carried  out  under  the  auspices  of  the  Indus- 
trial Society  of  Mulhouse,  whose  "  Bulletin"  (already  referred  to) 
contains  the  records. 

Even  with  calorimetric  estimations  of  heating  power,  con- 
siderable variations  from  the  calculated  or  theoretical  figures 
have  been  obtained,  as  is  shown  by  the  following  Table  of 
examples  of  the  results  obtained  by  Messrs.  Scheurer-Kestner 
and  Meunier-Dollfus1  and  published  by  them  and  by  Dr.  Percy  :2 


TABLE  XI. 


Percentage  composi- 
tion of  the  Coal 

Calorific  Power 
calculated  on 

Coke 

Exclusive  of 

the  dry  Coal 

pr.  cent, 
calcu- 

Ash and  Water. 

free  from  Ash. 

Description 

T 

lated  on 
the  dry 

of 
Coal. 

Hv- 

Oxygen 

Experi- 

Theo- 

Coal 
free 

Carbon. 

JiJ 

dro- 

and 

Nitro- 

mental 
Calo- 

retical 
Calo- 

from 
Ash. 

gen. 

gen. 

ries. 

ries. 

! 

Lignite 

Manosque,  Basses  Alpes 

66-31 

4-85 

28-84 

6991 

5782 

46-76 

2 

„ 

»          ))          » 

70-57 

5-44 

23-99 

7363 

6533 

47-55 

3 

not  stated 

Louisenthal,  Saarbriick 

76-87 

4-68 

I8'45 

8215 

7056 

59'49 

4 

»                 J> 

Duttweiler,  Saarbriick 

83-82 

4-60 

II-58 

8724 

7871 

63-58 

5 

M                 )> 

Ronchamp 

88-38 

4-42 

7-20 

9117 

8354 

7r58 

6 

Caking 

Creusot 

88-48 

4-41 

7-II 

9622 

8384 

80-42 

7 

non-caking 

>» 

90-79 

4-24 

4-97 

9293 

8585 

84-12 

8 

Anthracite 

. 

92-36 

3-66 

3-98 

9456 

8553 

88-15 

These    results    exhibit    differences   of   a    striking    character 
between  the  theoretical  and  experimental  calorific  power  in  all 

1  Annal.  de  Chim.  et  de  Phys.  3.4.,  1870,  xvi.,  p.  436  ;  8.4  1872,  xxvi.,  p.  80  ; 
see  also  M.  L.  Griiner's  "  Pouvoir  Calorifique  et  Classification  des  Houilles," 
Ann.  des  Mines,  1874,  p.  169. 

2  "  Metallurgy,"  Vol.  Fuel,  p.  539. 


THE  MODERN  STEAM  BOILER.  57 

cases,  and  also  differences  in  value  between  specimens  having 
practically  the  same  ultimate  composition  on  analysis.  Of  these 
latter  Nos.  5  and  6  are  examples,  whilst  6  and  7  show  other 
variations  and  anomalies  in  calculation  from  chemical  composi- 
tion. In  all  these  cases  which  are  noted  in  this  Table,  the 
experimental  calorific  power  exceeded  that  obtained  by  calcu- 
lation from  the  chemical  composition,  and  the  excess  amounted 
in  some  cases  to  15  per  cent.  In  fact  it  may  be  taken  as  almost 
a  general  rule  that  higher  heating  effects  may  be  obtained  from 
fuel  than  a  calculation  of  calorific  power  according  to  the  usual 
methods  would  cause  us  to  expect.  It  must  not  be  assumed, 
however,  that  the  thermal  value  yielded  by  experiment  with  a 
small  quantity  of  coal  burned  in  a  calorimeter  is  necessarily  the 
correct  one,  or  is  invariably  the  same  even  for  the  same  coal. 
There  are  several  sources  of  error  in  this  method,1  even  with  the 
best  calorimeter  in  use,  but  it  frequently  yields  higher  results' 
than  calculation  affords. 

Theoretical  Temperature  of  Combustion. — The  employment  of  air 
in  combustion  necessarily  exerts  a  considerable  influence  upon 
the  temperature  which  is  produced.  If  we  had  carbon  burning 
in  pure  oxygen,  the  hypothetical  maximum  temperature  which 
could  be  produced  would  be  : — 

p  P  being  the  calorific  power  of  carbon 

=  y&  =  8080. 

8080  36  being  the  quantity  of  carbonic  acid 

=  T6  x  0*2164  produced  per  equivalent  of  carbon. 

=  10,183°  Cent.         s  ^emg  the  specific  heat  of  carbonic 
acid. 

That  is  the  result  under  the  supposition  that  the  carbonic  acid 
as  produced  remains  under  constant  pressure.  Should  the 
volume  be  kept  constant  instead  of  the  pressure,  Dr.  Percy2  has 
stated  that  the  result  will  be  greater  in  the  ratio  of  i  to  1*265, 
and  hence  that  T  will  become 

10,183x1-265  =  12,881°  Cent. 

When  air,  supposed  to  consist  exclusively  of  oxygen  and  nitrogen, 
is  substituted  for  oxygen,  and  the  quantity  employed  is  that 

1  As  to  this,  see  "  On  the  Calorific  Value  of  Solid  and  Liquid  Fuels,"  Jour. 
Soc.  Chemical  Industry,  March  31,  1888  ;  also  ibid.  31  Oct.,  1901,  p.  972. 

2  "  Metallurgy,"  vol.  Fuel,  p.  168. 


5»  THE  PRACTICAL  PHYSICS  OF 

which  contains  the  exact  proportion  of  oxygen  required  for  the 
formation  of  carbonic  acid,  these  temperatures  become  corres- 
pondingly 

at  constant  pressure=27i8°Cent.,  and 

at    constant  volume  =  3438°  Cent. 

Similarly,  the  hypothetical  maximum  temperatures  produced  by 
the  combustion  of  hydrogen  appear  to  be  l 

in  oxygen,  under  constant  pressure =6743°  Cent. 

„  „  „         volume  =8779°  Cent, 

in  air,  under  constant  pressure         =2684°  Cent. 

„         „         „         volume  =3495°  Cent. 

Effects  of  Air. — It  will  readily  be  understood  that  the  tempera- 
tures obtainable  in  furnaces  from  the  combustion  of  fuel  must 
necessarily  be  considerably  below  these  figures.  Atmospheric 
air  is  a  more  complex  mixture  than  in  the  case  supposed  above, 
being  said  to  consist  by  volume  of 

0788N  +  0-1970  +  o-ooiCO2 
and  by  weight    o77iN  +  o'2i8O  +  o-oo9CO2 

so  that  the  deductions  to  be  made  from  the  maximum  hypo- 
thetical temperature  are  greater  than  those  given.  Then  again, 
the  practical  conditions  under  which  combustion  of  fuel  takes 
place  are  such  that  it  has  always  been  found  necessary,  for 
complete  combustion,  to  employ  a  greater  or  less  excess  of  air 
over  the  quantity  theoretically  required  to  supply  oxygen 
equivalent  to  the  carbon  and  hydrogen  in  the  fuel.  This  total 
quantity  of  air  has  to  be  heated  to  the  temperature  of  the  furnace, 
at  the  expense  of  the  available  heat  from  the  fuel,  and  moreover, 
the  large  volume  of  gases  resulting  usually  carries  off  a  by  no 
means  inconsiderable  proportion  of  this  heat,  part  only  being 
utilised  in  the  so-called  "  ascensional  power  "  of  the  gases,  due 
to  their  expanded  volume  and  correspondingly  reduced  weight. 

The  following  Table,  which  was  published  in  an  interesting 
paper  by  Mr.  W.  H.  Maw  ("  On  Methods  of  Producing  High 
Temperatures,"  Proc.  Inst.  Cleveland  Engineers),  some  years 
ago,  exhibits  some  of  these  facts  in  a  convenient  form.  The 
:iumber,  14,000,  of  heat  units  on  the  British  scale  has  been 

1  See  Percy's  "Metallurgy,"  Vol.  Fuel,  pp.  167-173. 


THE  MODERN  STEAM  BOILER. 


59 


adopted  for  carbon,  and  the  temperatures  are  given  in  Fahrenheit 
degrees  : 

TABLE  XII. 


Condition  of  conibustion. 

No.  of 
units 
of  heat 
produced. 

Weight  of 
products 
of 
combustion. 

Mean 
specific 
heat  of 
products 
of 
combustion. 

Increase  of  temperature 
produced. 

i  lb.  of  carbon  burnt  into  carbonic  } 
dioxide.      Oxygen   supplied   in   a  V 
pure  state.                                           ) 

i  lb.  of  carbon  converted  into  car-"| 

14,000 

lb. 
31 

O'2l6 

14.000     =  I7|6?60  F 
3§  x  0-216 

4-000       _AQI2oF 

bon  monoxide.    Oxygen  supplied  >• 
in  a  pure  state.                                   ) 

4,000 

2i 

0-248 

2l  X  0-248 

14,000     _          o  F 

supplied  in  atmospheric  air.             } 
i  lb.  of  carbon  converted  into  CO.  \ 

14,000 
4.OOO 

13 
7 

0-237 
0-254 

13  x  0-237 

4,000       _  ^          o  p 

i  lb.  of  carbon  burnt  to  CO2.  Oxygen  \ 
supplied    in    air    20   per  cent   in  > 

14,000 

i5§ 

0-237 

7  x  0-254 
14,000      _    g  ,0  F 

excess.                                                  ) 

i  lb.  of  carbon  burnt  to  CO...    Oxygen  \ 
supplied    in    air  50   per  cent,   in  > 

14,000 

iQ 

0-237 

15-4  x  0-237 
14,000     _          op 

excess.                                                  J 

19  x  0-237 

Loss  of  Heat  from  Opening  Furnace  Doors. — There  is  another 
cause  of  loss  of  heat,  or  failure  to  obtain  the  full  result  possible 
from  a  given  fuel,  the  extent  of  which  is  very  seldom  estimated, 
and  that  is  found  in  the  frequent  opening  of  furnace  doors  as 
required  in  the  ordinary  processes  of  stoking.  In  no  furnaces 
are  the  evil  effects  of  this  so  likely  to  be  quickly  experienced  as 
in  steam  boiler  furnaces,  on  account  of  the  limited  amount  of 
lire  brick  surface  and  the  large  amount  of  metal  surface  exposed 
to  the  action  of  the  flame  and  hot  or  cold  gases.  Each  time  the 
doors  are  opened  there  is  an  inrush  of  comparatively  cold  air 
from  the  stokehold,  with  consequent  dilution  of  the  hot  gases  and 
general  reduction  of  the  temperature  ;  and  if  Mr.  Yarrow's 
estimate  of  1,440  such  openings  in  24  hours  (referred  to  in 
chap.  II.  ante)  is  at  all  near  the  mark,  the  loss  of  heat  from  this 
cause  must  be  enormous. 

Fluctuations  of  Temperature  in  Furnaces. — It  has  been  recently 
said1  that  "  when  calculations  are  made  for  the  transmission  of 

1  "  On  the  the  Transmission  of  Heat  through  Plates  from  Hot  Gases  to 
Water,"  by  Mr.  George  Halliday.  Trans.  Inst.  Engineers  and  Shipbuilders  in 
Scotland,  Vol.  xlii.,  p.  41. 


6o 


THE  PRACTICAL  PHYSICS  OF 


heat  through  plates  for  a  constant  temperature  of  furnace  and 
chimney,  it  must  be  understood  that  no  such  thing  exists  in 
practice,  the  temperature  changing  in  the  furnace  200°  F.  in  less 
than  a  quarter  of  an  hour,  and  the  chimney  varying  within  100° 
in  about  the  same  time."  It  is  probable,  however,  that  Mr. 
Halliday's  estimate  is  considerably  below  the  mark.  The 


ffTM 


33. 


diagrams  (see  Figs.  33,  34,  35,  and  36)  of  fluctuations 
of  temperature  in  Mr.  Houldsworth's  trials,  with  carefully 
regulated  hand  stoking  and  chimney  draught,  show  fluctua- 
tions of  400°  F.  due  to  opening  firing  doors  and  charging 
fuel  every  half  hour  ;  and  where  the  fire  was  stirred  between 
charges,  the  temperature  did  not  again  rise  to  its  former  point 


ft  AM. 


ffPM 


FIG.   34- 

after  each  charge,  so  that  it  was  on  the  average  on  a  continual 
down  grade.  These  diagrams  were  originally  communicated  to 
the  Select  Committee  on  Smoke  Prevention  in  1843,  and  are 
reproduced  in  Mr.  D.  K.  Clark's  "  Steam  Engine  "  (Vol.  i.,  pp. 
206-213).  In  Mr.  Yarrow's  estimate  of  the  frequency  of 
opening  furnace  doors,  a  large  marine  boiler,  worked  with  forced 


THE  MODERN  STEAM  BOILER. 


61 


draught,  is  supposed,  where  consequently  the  combustion  would 
be  more  rapid,  and  the  necessity  for  charging  and  stirring  fires 
more  frequent.1 


JlA.Af  12 


1100' 


100V 


SCO' 


i 


800' 


7#r 


60CT 


SOT 


400'' 


Average 


/tea/-  aJjoiU 


300" 


FIG.  35. 


FIG.  36. 


Various   estimates   of  the   actual   temperatures   produced  in 
furnaces  have  been  formed,  and  pyrometrical  tests  have  been 


1  Refer  also  to  D.  K.  Clark,  "  The  Steam  Engine,"  Vol.  i.,  p.  295. 


62  THE   PRACTICAL  PHYSICS  OF 

made  by  Mr.  Isherwood,  Mr.  W.  A.  Martin,  Mr.  John  Elder, 
Mr.  D.  K.  Clark  and  others,  but  most  of  these  suffer  in  their 
value  from  the  exceedingly  imperfect  apparatus  necessarily 
employed.  With  the  pyrometers  of  Le  Chatelier  and  of  H.  L. 
Callendar,  there  is  now  a  much  better  opportunity  than  has  ever 
previously  occurred  of  obtaining  continuous  and  accurate  records 
of  high  temperatures.1 

Quantity  of  Air  Employed,  —  Whilst  12*2  Ibs.  of  air  supply  the 
quantity  of  oxygen  sufficient  for  the  combustion  of  i  Ib.  of 
carbon,  it  has  been  found  that,  with  chimney  draught,  as  much 
as  from  1  8  to  22  Ibs.  of  air  per  Ib.  of  coal  are  necessary  for  the 
complete  combustion  of  coal  with  ordinary  grates  and  chimney 
draught,  so  that  the  presence  of  unconsumed  carbon  monoxide 
in  the  waste  gases  may  be  prevented.  This  is  well  illustrated  in 
the  tabulated  results  of  trials  given  by  Prof.  Kennedy  and  Mr. 
Bryan  Donkin  in  "  Evaporative  Trials  of  Steam  Boilers."  With 
the  ordinary  systems  of  forced  draught  in  use  there  seems  to 
have  been  little  reduction  made  in  that  quantity,  unless  with 
water-tube  boilers,  which  have  shown  17-2  to  18*1  Ibs.  of  air  per 
Ib.  of  coal  with  a  fair  economy  in  the  consumption  of  fuel  per 
I.H.P.  hour. 

Effects  of  Different  Quantities  of  Air.  —  The  following  diagram 
was  constructed  by  Mr.  (afterwards  Sir)  William  Anderson  to 
exhibit  graphically  the  effects  produced  on  the  temperature  of 
combustion  by  the  addition  of  different  proportions  of  air  to  the 
fuel.  Taking  12*2  Ibs.  of  air  and  5150°  absolute  (calculated 
thus— 


T  =  520°  +    J4,54_4  uns_=  0  absolute) 

13-2  Ibs.  x  0-238 

as  the  theoretical  temperature  of  combustion,  with  that  quantity 
for  a  starting  point,  the  curve  for  carbon  shows  the  probable 
temperature  with  successive  additions  of  air,  making  totals  of 
18-3,  24-4,  and  36*6  Ibs.  of  air  per  Ib.  of  carbon.  These  quanti- 
ties of  air  are  set  up  as  vertical  ordinates  to  the  base  line  in 
Fig.  37,  the  base  line  representing  absolute  zero  and  the 
horizontal  lines  above  it  various  degrees  of  temperature  on  the 

1  See  also  "  The  Pneumatic  Pyrometer,  with  Autographic  Recorder,"  by 
E.  A.  Uehling.  Cleveland  Instn.  of  Engineers.  January  22,  1900.  Arndt's 
Apparatus.  A.  Bement.  Jour.  West.  Soc.  Engineers,  Vol.  vi.,  pp. 
204-210. 


THE  MODERN  STEAM  BOILER.  63 

absolute  scale,  those  for  the  melting  points  of  steel,  of  different 
kinds  having  been  carefully  found.  The  upper  curve  illustrates 
similarly  the  combustion  temperatures  of  petroleum  composed 
of  0*84  of  carbon  and  O'i6  of  hydrogen,  i  Ib.  of  the  oil  requiring 
only  10*32  Ibs.  of  air  theoretically  for  its  complete  combustion, 
and  yielding  with  it  22,136  British  heat  units.  The  ordinates  in 


iS       4000° 
|.      3551' 

3000" 
2456' 


\ 
<v 

032      \ 


183 


PETROLEUM 
JO-36LBS  OF 

AIR 


CARBON 

36  €  LBS.OF 

AIR 


2 
FIG.  37- 


Quantity 
3    of  air  ad- 
mitted. 


this    case    represent   additions  of    air  in  quantities  which  are 
multiples  of  10-32  Ibs. 

Volume  of  Gases  from  Combustion. — Professor  Rankine  calcu- 
lated the  volume  of  gases  from  the  combustion  in  a  furnace  at 
temperatures  from  32°  to  4640°  Faht.  on  the  basis  of  12  Ibs.  of 
air  per  Ib.  of  fuel  being  supplied,  and  also  at  18  Ibs.  and  24  Ibs. 
of  air  per  Ib.  of  fuel.  Ignoring  variations  of  density  produced 
by  fluctuations  of  the  pressure  of  gases  in  the  furnace,  above  or 
below  the  mean  atmospheric  pressure,  he  assumed  the  volume 


64  THE  PRACTICAL  PHYSICS  OF 

at  32°  Fahr.  to  be  12 \  cubic  feet  for  each  Ib.  of  air  supplied  to 
the  furnace,  so  that  with — 

12  Ibs.  of  air  supplied  per  Ib.  of  fuel,  the  volume  of  gases  at  32° 
per  Ib.  of  fuel  would  be  ...          ...          ...     150  cubic  feet. 

with  18      ...          ...     225     ,,         „ 

„     24      ...  ...     300     „ 

The   volume   at   any    other   temperature  T  is    calculated   as 
follows  :— 

V  =  volume  at  32°  x  T  +  4^°'2  =  V0.  L 


V0  being  =  the  volume  at  32°  of  air  supplied  per  Ib,  of  fuel. 

T      „       =  the  temperature  T  on  the  absolute  scale.1 

ro     )f       =  the  absolute  temperature  of  melting  ice,  i.e.  493°'2. 

The  results  obtained  by  means  of  this  calculation  are  given  in 
Table  XIII. 

The  velocity  of  the  current  of  these  gases  in  a  chimney  in  feet 
per  second  is  reckoned  as  follows  :  — 

_ 

w  being  =  the  weight  of  fuel  burned  in  the  furnace  per  sfecond. 
V0     ,,     =  the  volume  at  32°  of  the  air  supplied  per  Ib.  of  fuel. 
T-J      ,,     =  the  absolute  temperature  of  the  gases  discharged  by 

the  chimney. 
A     ,,      =  the  sectional  area  of  the  chimney. 

1  Absolute  Temperatures.    (Rankine  "  Steam  Engine,"  p.  228).    The  absolute 
zero    is    the  imagined  temperature  corresponding  to  the  disappearance  of 
gaseous  elasticity,  at  which  pv  =  o.     Temperatures  reckoned  from  that  point 
are  called  absolute  temperatures,  and  denoted  by  the  symbol  T. 
Let  r0  be  the  absolute  temperature  of  melting  ice. 

Let  TI  be  the  absolute  temperature  of  boiling  water  at  atmospheric  pressure. 
Let  T  be  any  third  absolute  temperature. 

Then 

_  T 


pv 
For  Fahrenheit   scale   r0=493°'2  ;    r1=673°'2  ;  °- 


For  Centigrade  scale  r0=274°;  r1=374°  J  r=274°^o= 

The  position  of  absolute  zero  on  the  Fahrenheit  scale  is  —  46i°'2. 
The  position  of  absolute  zero  on  the  Centigrade  scale  is  —  274°. 


THE  MODERN   STEAM  BOILER. 

TABLE  XIII. 


65 


Temperature. 

Volume  of  gases  per  Ib.  of  fuel,  in  cubic  feet, 
when  air  supply  in  Ibs.  of  air  per  Ib.  of  fuel  is 

12  Ibs. 

18  Ibs. 

24  Ibs. 

32°  Fahr. 

150  cub.  ft. 

225  cub.  ft. 

300  cub.  ft. 

68°       „ 

161       „ 

241       » 

322       „ 

104°       „ 

172             „ 

258       „ 

344       „ 

212°         „ 

205     „ 

307              M 

409       „ 

392°         „ 

259              M 

389              „ 

519       „ 

572°         „ 

314     „ 

471               » 

628       „ 

752°         „ 

369    „ 

553       „ 

738       „ 

1112°         ,, 

479       „ 

7i8       „ 

937       „ 

I4720         „ 

588       „ 

882       „ 

1176       „ 

"             • 

697       „ 

1046       „ 

1395       „ 

2500° 

906       ,,       ' 

1359      ,, 

1812 

3^75°     „ 

1136       „ 

1704       „ 

4640°     „ 

1551       „ 

The   density   of   that    current    in    Ibs.    to    the    cubic   foot  is, 
according  to  Rankine,  very  nearly 


D  =—  f  0-0807  + — 

or  from 

0-084  t°  0-087  x  ro  ~i~  T\ 

To  calculate  the  "  head,"  or  height  in  feet,  of  a  column  of  the 
hot  gases  in  the  chimney,  which  is  required  to  produce  the 
velocity  u,  Rankine  uses  the  formula  and  constants  given  by 
Peclet— 


2g  m 

G  being  a  factor  of  resistance  to  air  passing  through  the  fuel 
on  a  grate  ascertained  by  Peclet  to  be  12  for  furnaces  burning 
from  20  to  24  Ibs.  of  coal  per  square  foot  of  grate  ; 

/being  a  co-efficient  of  friction  estimated  at  0*012  by  Peclet  ; 

m  being  the  hydraulic  mean  depth  of  chimney  or  one  fourth 
of  the  diameter  of  a  round  chimney  ; 

/  being  the  whole  length  of  the  chimney  and  flue  in  feet. 


66  THE  PRACTICAL  PHYSICS  OF 

The  formula  then  becomes — 

h 

13 


The  head  may  be  converted  into  an  equivalent  pressure  in  Ibs. 
per  square  foot  by  multiplying  it  by  the  density  as  given  above, 
i.e.  p=hD,  and  this  may  be  converted  into  any  other  unit  of 
pressure  by  multiplying  by  a  suitable  factor. 

For  head  in  inches  of  water  the  multiplier  is  —  —  =  0-102,  so 

5-204 

that  head  in  inches  of  water=o'i92/>  or  0*192  hD. 

One  Ib.  on  the  square  inch  =2-307  feet  of  water. 

The  following  particulars  of  speed  of  gases  with  natural 
draught  are  taken  from  M.  Bertin's  work  on  "  Marine  Boilers." 

"  A  column  of  air  at  572°  has  a  specific  weight  of  about  half  that  of  the 
external  atmosphere.  If  H  be  the  height  of  the  funnel  above  the  grate  bars, 
and  the  velocity  be  taken  as  uniform,  the  depression  at  the  base  of  the  funnel 
would  iH. 

"  Expressing  this  in  inches  of  water,  we  have  :  —  \ 

00000466 


0*03611 

when  H  equals  the  height  of  the  funnel  in  feet,  and  h  the  height  of  the  water 
column  in  inches.  The  weight  of  I  cubic  in.  of  air  at  32°  F.  is  0-0000466  lb.; 
and  that  of  i  cubic  in.  of  water  0-03611  Ib. 

"  Thus  at  the  base  of  a  funnel  66  ft.,  49  ft.,  or  33  ft.  high,  the  depression 
will  amount  to  0-53  in.,  0*39  in.,  or  0-26  in.  of  water  respectively,  on  the 
supposition  that  the  mean  temperature  of  the  gases  is  572°  F.,  and  that  the 
movement  of  the  column  of  air  is  not  obstructed. 

"  It  has  been  observed  that  the  velocity  of  the  air  is  1273  ft.  on  entering  the 
ash  pans  for  a  depression  of  0-52  in.  in  the  ash  pans,  which  corresponds  to  a 
depression  of  0-43  in.  in  the  furnace.  If  the  air  spaces  between  the  furnace 
bars  are  equal  to  60  per  cent,  of  the  grate  surface,  or  say  three  times  the  section 
of  the  ashpit  doors,  the  speed  of  the  air  though  the  bars  will  only  be  about 
4-26  feet. 

"  Calculating  the  depression  for  a  speed  of  1273  feet,  we  have  :  — 

T  2*71^ 

A//=  —  ^L  =  0-023  in. 
6900 

a  very  small  fraction  of  the  whole  draught. 

"At  the  base  of  the  funnel  the  velocity  of  the  gases  is  much  greater  than 
through  the  ashpans,  on  account  of  the  reduced  section,  and  also  that  the 
volume  of  the  gases  is  increased,  due  to  the  increased  temperature. 

"  To  the  weight  of  the  column  of  air  must  be  added  also  the  weight  of  the 
products  of  combustion. 

"  Supposing  the  section  of  the  funnel  to  be  three-quarters  of  the  section 
through  the  ashpits,  the  volume  of  the  gas  will  be  doubled  when  raised  to 
572°,  and  therefore  the  speed  will  be  2'66  times  that  through  the  ashpits.  The 
increase  of  weight,  amounting  to  about  JQ>  may  be  neglected.  The  value  of 
A  h,  therefore,  at  the  base  of  the  funnel  may  be  taken  to  correspond  to 
about  :  — 

0*023  X  2-662  =  o-i6. 


THE  MODERN  STEAM  BOILER. 


67 


"  The  energy  absorbed  in  putting  the  column  of  gases  in  motion  is  small 
compared  with  that  absorbed  in  overcoming  the  resistance  of  obstructions. 
Neglecting  the  resistance  due  to  the  ashpits,  which  is  not  great,  the  draught 
of  0-51  may  be  divided  up  as  follows  for  a  return  tube  boiler  : — 

Resistance  due  to  funnel,  uptakes,  and  smoke  box...         ...     O'O2  in. 

„  „         tubes  o-ii    ,, 

,,  ,,         firebox,  bridge,  furnace    ...         ...         ...     o-o6    ,, 

„  „         fire  of  moderate  thickness  ...         ...     0*31    ,, 

,,  ,,         inertia  of  column  of  gases  ...         ....     0*02    ,, 

Total     ...     0-51 

"  In  that  division  the  total  draught  is  measured  from  the  fire-bars,  neglecting 
the  height  of  the  smoke  box  where  the  draught  is  usually  measured.  The 
actual  readings  on  the  gauge  would  be  O'O2  in.  in  the  ashpit,  0^33  in.  in 
the  furnace,  0-39  in.  in  the  combustion  chamber  at  the  back  tube  plate,  and 
0-51  in.  in  the  smoke  box.  As  a  matter  of  fact  the  movement  of  the  gases  is 
by  no  means  uniform  and  is  subjected  to  great  fluctuations.  The  following 
Table  gives  approximate  velocities  at  various  points,  the  grate  area  being  taken 
as  unity  : — 

TABLE  XIV. 


Section. 

Temperature 
Degrees  F. 

Approximate 
Velocity. 

Ashpan  doors  ... 

0'2 

86 

Ft.  per  sec. 
I3'I2 

Air  passages  through  grate  ... 

0'33 

Air  passages  through  the  coal 
Area  above  bridge 

0'2I 

(assumed) 

O'2I 

2912 
2192 

91-86 
7^46 

Combustion  chamber 

0-21 

1742 

62-34 

Entrance  to  tubes  at  back  tube-plate 

0-l8 

1292 

49-21 

Exit  to  tubes  at  front  tube-plate     
Funnel 

0-18 

O'l^ 

662 
^72 

32'8l 

"  In  tubulous  boilers  the  section  for  the  gases  is  generally  very  large  when 
the  gases  leave  the  grate.  Baffles  are  often  employed  to  reduce  the  section 
and  increase  the  length  of  the  course  of  the  gases  through  the  tubes.  Even 
with  natural  draught  the  gases  sometimes  reach  the  funnel  too  quickly.  The 
bottom  of  the  funnel  which,  under  these  conditions,  is  at  a  temperature  of  about 
932°  F.,  becomes  a  dull  red  and  greatly  increases  the  draught.  This  gives 
rise  to  the  entry  of  an  excess  of  cold  air,  and  thereby  reduces  the  efficiency  of 
combustion.  In  a  boiler  where  the  gases  have  too  short  a  course,  too  high 
a  funnel  may  lead  to  bad  combustion,  but  in  general  it  is  advisable  to  have  a 
high  funnel." 

Effects  of  Pre- heating  the  Air  for  Combustion. — The  economical 
effects  of  utilising  the  waste  heat  of  the  products  of  combustion 
for  pre-heating  the  air  which  is  introduced  for  burning  the  fuel 
have  not  been  fully  realised.  There  is  no  doubt  that  one  of  the 

D2 


68  THE  PRACTICAL  PHYSICS  OF 

advantages  derivable  from  the  use  of  forced  combustion  or 
mechanically  produced  air-supply,  is  to  be  found  in  the  facility 
which  it  offers  for  this  preliminary  heating  of  the  air.  The  plan 
of  a  closed  stokehold,  however,  used  in  vessels  of  the  British  Navy, 
does  not  lend  itself  to  the  process,  as  it  would  be  manifestly 
impossible  to  raise  the  atmosphere  of  the  stokehold  in  which 
men  work  to  anything  like  a  high  temperature.  Methods  of 
suction  draught  are,  however,  quite  as  suitable  as  other  plans 
for  the  addition  of  preliminary  heating  of  the  air  supply  for  the 
furnaces,  and  these  elements  have  been  combined  in  one  case  at 
least.  Wherever  it  is  possible  to  introduce  it,  the  increase  of 
efficiency  which  may  be  realised  from  such  pre- heating  is 
undoubted. 

In  the  case,  for  instance,  of  a  pound  of  carbon  burned  to 
carbonic  acid  (referred  to  in  Table  XII.  on  page  59)  with  a  supply 
of  air  amounting  to  20  per  cent,  in  excess  of  the  theoretical 
quantity  required  for  oxidation,  and  showing  a  theoretical  result- 
ing temperature  of  3836°  F.,  the  effect  produced  by  supplying 
the  air  for  combustion  heated  (by  means  of  the  waste  heat  from 
chimney  gases)  to  400°  above  the  normal  atmospheric  tempera- 
ture, is  considerable.  It  will  amount  to  14*4  x  400  x  0*238,  or  about 
1371  units  of  heat  added  to  the  furnace  per  Ib.  of  carbon  burnt. 

The  resulting  temperature  should  in  that  case  be — 

14000  +  1371  =  .15371  =      o  paht 

15-4  x  0-237         3-6498 

showing  an  increase  of  375°  F.  in  the  temperature  as  compared 
with  that  produced  without  the  preliminary  heating  of  the  air. 
In  a  paper  "  On  Chimney  Draught  and  Forced  Combustion,"  1  by 
the  author,  another  estimate  was  given.  Supposing  i  Ib.  of 
average  Newcastle  coal  to  be  capable  of  yielding  10,000  heat 
units  and  to  be  supplied  with  24  Ibs.  of  air  for  combustion 
which  is  heated,  by  transference  of  heat  from  the  waste  gases,  to 
a  temperature  of  300°  F.  above  the  atmospheric  temperature, 
then  the  result  would  be  300  x  '2374  (i.e.,  the  specific  heat  of  air) 
=  71  units  x  24  (the  air  used  for  combustion)  =  1704  units,  or  17 
per  cent,  would  be  added  to  the  10,000  units  produced  with  air 
of  normal  temperature.  Similarly  if  the  temperature  of  the  air 

1  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scot.  Vol.  xxxii.  (Dec.,  1888.)  See 
also  "  On  Combustion."  Jour.  Soc.  Chem.  Ind.  Vol.  1883,  p.  79. 


THE  MODERN  STEAM  BOILER.  69 

supply  were  increased  by  600°  and  1000°  F.,  the  augmentation 
of  efficiency  would  be  respectively  24^  and  57  per  cent.  In 
other  words,  with  an  air  supply  exceeding  the  normal  atmos- 
pheric temperature  by  300°,  600°  and  1000°  F.,  17  cwts.,  15  cwts., 
and  9  cwts.  of  coal  would  respectively  perform  the  duty  of  i 
ton  if  burnt  with  a  similar  weight  of  air  at  ordinary,  temperature. 
Plans  for  pre-heating  the  air  used  for  combustion  have  been  in 
use  in  ordinary  furnaces  and  in  gas  furnaces  on  land  since  1843, 
as  may  be  seen  by  reference  to  the  following  works  :  Dr. 
Percy's  "  Metallurgy,"  Vols.  "  Fuel,"  p.  518  ;  "  Iron  and  Steel," 
p.  716  ;  Tunner's  "  Eisen-hiittenwesen  in  Schweden  "  :  D.  K. 
Clark's  "  Fuel,  its  Combustion,  etc."  ;  Mills  and  Rowan's  "  Fuel 
and  its  Applications."  pp.  660-692,  etc.,  whilst  the  value  of  heated 
blast  in  iron  smelting  furnaces  has  been  elaborately  worked 
out  by  Sir  I.  Lowthian  Bell.1  In  Sennett  and  Gram's  work  on 
"The  Marine  Steam  Engine"  (1898)  it  is  stated  that  "  the 
development  of  the  air-heating  principle  in  this  country  is  due 
principally  to  Mr.  Howden  of  Glasgow,"  but  it  is  evident  that 
(as  perhaps  the  authors  meant)  this  statement  applies  only  to 
the  combination  of  such  apparatus  with  forced  draught  in 
marine  boilers  with  the  ordinary  grate  or  internal  furnace. 

Temperature  of  Exit  Gases. — Another  point  which  demands  con- 
sideration is  that  of  the  temperature  at  which  the  waste  gases 
are  allowed  to  escape  into  the  air,  as  this  temperature  determines 
the  quantity  of  heat  which  is  uselessly  dissipated,  and  thus  fixes 
the  lower  limit  from  which  the  useful  effect  of  the  fuel  or  boiler 
can  be  calculated. 

Taking  the  average  quality  of  Newcastle  coal  as  above  for  an 
example,  with  24  Ibs.  of  air  per  Ib.  of  coal  for  combustion,  the 
waste  gases  wrould  amount  to  25  Ibs.,  with  the  following  result 
as  to  heat  absorption  :  i.e. 

Specific          Heat 
Gases.  Ibs.  heat.  units. 

Carbon  dioxide          ...          ...          3*7    x    '217   =   '8029 

Oxygen          2*8    x    -218   =   '6104 

Nitrogen         18-5    x    '244  =4-5140 

25'°  =5'9273 

heat  units  required  to  raise  these  gases  i°  Faht. 

1  See  '•  Principles  of  the  Manufacture  of  Irun  and  Steel,"  by  I.  Lowthian 
Bell,  F.K.S.  London, 


70  THE  PRACTICAL  PHYSICS  OF 

Consequently  if  these  gases  were  discharged  into  the  chimney 
at  600°  F.  above  the  initial  atmospheric  temperature,  5*9273  x 
600=3556  heat  units  out  of  a  possible  10,000,  or  35^  per  cent, 
would  be  entirely  lost  or  absorbed  in  draught  production.  If 
these  gases  were  discharged  at  iooo9  F.  above  the  atmosphere, 
the  loss  with  the  same  consumption  of  air  would  reach  5927 
heat  units,  an  amount  considerably  exceeding  one  half  the  entire 
calorific  value  of  the  fuel.1 

With  draught  produced  only  by  means  of  the  ascent  of  hot 
gases  in  the  chimney,  the  temperature  which  it  is  considered 
most  advantageous  (from  the  point  of  view  of  draught  produc- 
tion) for  these  gases  to  have  is  600°  F.  In  certain  cases,  how- 
ever, as  for  instance  in  that  of  the  boilers  of  the  s.s.  "  Pro- 
pontis,"  and  other  examples  of  the  same  plans,2  a  chimney 
temperature  of  not  more  than  480°  F.  was  obtained,  along  with 
the  best  results  as  to  economy  in  consumption  of  fuel  in  these 
boilers,  which  was  due  to  their  having  a  very  large  proportion 
of  heating  surface  per  horse  power  and  being  wrought  with  slow 
combustion. 

In  some  marine  boilers,  worked  with  forced  or  mechanically 
produced  (sometimes  called  "  accelerated  ")  draught,  either  air- 
heaters  or  feed- water  heaters  (or  "  economisers ")  have  been 
introduced  in  the  uptakes  or  upper  portions  of  the  boiler 
casings,  or  in  the  space  immediately  above  the  boiler  and 
between  it  and  the  chimney,  in  order  to  lower  the  temperature 
of  the  escaping  gases  as  much  as  possible.  Where  feed-water 
heaters  alone  are  used  it  is  apparent,  as  Mr.  Anderson  remarked 
in  his  lecture3  on  "  The  Generation  of  Steam  and  Thermodynamic 
Problems  Involved,"  that  the  chimney  temperature  cannot  be 
lowered  below  the  temperature  of  the  feed  water,  and  the  limits 
of  economy  in  such  an  application  are  soon  reached. 

There  is  no  reason,  however,  why  both  kinds  of  heaters  should 
not  be  simultaneously  employed  in  order  to  utilise  as  much  of 
the  waste  heat  as  is  possible. 

1  Some  interesting  figures  on  the  subject  are  given  by  Mr.  Howden  in  his 
paper   on   "Forced   Combustion    in    Steam    Boilers."       Proc.    International 
Engineering  Congress,  Chicago,  1894.     Vol.  ii.,  Paper  No.  xlii.,  Page  12. 

2  See  "  On  the  Introduction  of  the  Compound  Engine  and  the  use  of  High 
Pressure  Steam,"  etc.,  by  F.  J.  Rowan.     Trans.  Inst.  Eng.  and  Shipbuilders  in 
Scotland.     Vol.  xxiii.,  p.  15. 

3  Proc.  Inst.  C.  E.,  1883-84. 


THE  MODERN  STEAM  BOILER.  71 

A  further  step  in  economy  of  heat  would  no  doubt  be  realised 
by  the  addition  of  an  auxiliary  air  condenser  to  the  main 
engines,  making  the  cold  air,  as  drawn  by  the  fans  or  blowers, 
to  pass  through  or  among  tubes,  having  the  exhaust  steam  from 
the  low  pressure  cylinders  in  contact  on  the  opposite  surfaces  of 
the  tubes,  and  thus  effecting  the  first  step  in  the  condensation 
of  the  steam  used  in  the  main  engines.  The  condensation 
would  have  to  be  completed  by  a  water  condenser,  but  as 
all  the  heat  removed  from  this  steam  in  the  usual  way — by 
means  of  circulating  water  in  condensers — is  lost  by  being 
carried  out  of  the  steamship  by  the  water,  it  is  clear  that  if 
a  portion  of  this  heat  could  be  returned  by  means  of  air  to  the 
furnace  from  which  it  was  originally  derived,  a  saving  would 
be  effected. 

A  proposal  was  made  some  years  ago  by  Mr.  J.  P.  Wilson l  to 
utilise  the  waste  steam  from  the  auxiliary  steam  engines  on 
board  ship  for  the  purpose  of  heating  air  for  combustion,  and 
experiments  made  'with  this  plan  were  said  to  have  given  good 
results.  There  is  no  reason  why  it  should  not  do  so,  or  why 
the  larger  quantity  of  heat  available  in  the  steam  from  the 
main  engines  should  not  also  be  used.  Mr.  James  Howden 
claims  to  have  proposed  an  air  condenser  with  this  object 
in  i86o.2 

Forced  or  Accelerated  Draught. — It  is  unnecessary  in  the 
present  state  of  engineering  science  to  urge  at  length  the  advan- 
tages of  forced  or  mechanical  as  against  chimney  draught.  In 
this  respect  there  is  a  great  contrast  between  the  present  time 
and  twenty  years  ago,  as  may  be  seen  by  a  perusal  of  some 
remarks  in  an  article  in  The  Engineer  of  3oth  August,  1878, 
page  152,  reviewing  the  author's  paper,  in  which  forced  com- 
bustion was  advocated.  A  statement  of  these  advantages  will 
now,  however,  help  to  point  out  the  way  to  further  improve- 
ment. With  mechanically  produced  draught  there  is  : — 

1.  A  considerable  economy  in  the  power  required  to  produce 
the  movement  of  the  air  and  gases. 

2.  A  greater  rapidity  and    therefore    increased    intensity    of 


1  See  Engineering,  15  April,  1887. 

*  See  Proceedings   of  the  International  Engineering   Congress,  Chicago, 
1894.     Vol.  ii.,  Paper  No.  xlii.,  page  14. 


72  THE  PRACTICAL  PHYSICS  OF 

combustion  is  possible,  by  which  means  higher  temperatures  are 
produced  in  the  furnace. 

3.  The  velocity  and  direction  of  travel  of  the  hot  gases  over 
the  heating  surfaces,  as  well  as  the  escape  of  the  waste  gases, 
can  be  controlled  without  difficulty. 

4.  The    incoming   air  for  combustion   can  be  made  to   pass 
through  heaters  exposed  to  waste  heat,  in  various  positions. 

5.  It  is  thus  possible  to  lose  or  reject  a  smaller  amount  of  heat 
in  the  gases  or  condensing  water  finally  expelled. 

Although  it  has  become  possible  to  burn  large  quantities  of 
fuel  per  square  foot  of  grate  surface  per  hour,  by  means  of  the 
use  of  accelerated  draught,  and  to  do  this  with  fairly  good 
results,  comparatively,  as  to  economical  evaporation  per  Ib.  of 
fuel  burned,  the  full  advantages  of  forced  combustion  have  not 
yet  been  reaped. 

Defects  of  Ordinary  Systems  of  Forced  Combustion. — The  propor- 
tion of  air  introduced  for  combustion  is  still  a  long  way  in  excess 
of  the  theoretical  quantity,  and  the  fluctuations  of  heat  in  the  fur- 
nace are  not  prevented,  but  in  many  cases  are  increased  in 
frequency.  And  finally  the  strain  thrown  upon  the  manual 
labour  of  stokers  has  been  very  greatly  increased,  and  thereby 
the  effect  of  the  uncertain  human  factor,  or  " personal  equation" 
of  the  stokers  on  the  realisation  of  pre-determined  results  has 
been  intensified.  All  the  drawbacks  experienced  with  the 
system  are  inherent  to  the  use  of  the  ordinary  fire  grates  placed 
inside  the  boilers.  These  inside  grates  also  render  the  applica- 
tion of  mechanical  methods  of  feeding  the  fuel  extremely 
difficult  of  introduction,  and  the  fluctuations  in  temperature  are 
such  that  no  very  good  result  has  been  reached  with  any 
boiler,  as  yet,  in  the  quantity  of  water  evaporated  per  unit  area 
of  heating  surface. 

External  Combustion  Chambers. — The  introduction  of  external 
combustion  chambers  will  cause  many  of  these  difficulties  to 
disappear  ;  the  coal  can  'be  continuously  fed  by  mechanical 
means  and  the  necessity  for  opening  firing  doors  will  be  entirely 
abolished  along  with  the  necessity  for  human  stokers.  As 
nothing  but  a  continual  stream  of  flame  and  hot  gases  need  be 
sent  inside  the  boiler  casing  and  throughout  the  heating  surface, 
the  evaporative  efficiency  of  that  surface  may  be  maintained  con- 
stantly at  its  highest  point,  always  provided  that  the  arrangements 


THE  MODERN  STEAM  BOILER.  73 

for  circulating  the  water  in  contact  with  that  surface  are 
adequate  and  efficient.  Finally  we  have  with  this  method  the 
opportunity  of  applying  combustion  under  increased  pressure, 
the  economic  value  of  which  has  not  been  as  yet  acknowledged, 
nor  have  attempts  been  made  -to  utilise  it  in  any  boiler  intro- 
duced hitherto. 

Economy  in  Power. — With  regard  to  the  economy  of  power 
represented  by  methods  of  forced  draught,  the  following  calcu- 
lation from  the  French  of  M.  Minary  was  given  in  u  Fuel  and  its 
Applications"  (pp.  385,  386).  It  is  known  that  gases  expand 
0*367  of  their  volume  for  each  100°  C.  elevation  of  temperature. 
If  we  suppose  the  air  \vhich  nils  a  chimney  suddenly  elevated 
200°  C.  in  temperature,  its  volume  will  become  I  +  (0-367  x  2)  = 
i '734.  The  internal  capacity  of  the  chimney  being  con- 
stant, all  the  increase  of  volume  due  to  expansion  escapes 
upwards. 

The  weight  of  a  cubic  metre  of  air,  which  at  o°  C  was   1*293 

kilo.,  becomes  at  200°  C  -  _2?^so*745  kilo  ;  it  has  thus  lost  0-548 

r734 
kilo,  per  cubic  metre. 

Suppose  a  chimney  of  a  square  metre  in  sectional  area,  and  of 
20  metres  height,  the  diminution  of  pressure  at  the  base  of  the 
chimney  will  be  for  200°  C.,  20  times  0-548,  or  10*960  kilos.,  cor- 
responding to  a  column  of  water  0*01096  of  a  metre,  or  nearly 
ii  millimetres  high,  which  is  the  pressure  at  which  the  air  will  be 
supplied  to  the  nre  or  furnace.  Under  the  influence  of  this 
pressure,  the  expanded  air  will  have  a  velocity  of  escape  equal 
to  16*94  metres  (equal  to  55*56  feet)  per  second,  after  making 
deduction  for  friction  and  for  resistance  offered  by  the  chimney 
walls  and  by  changes  of  direction  and  of  section. 

This  can  be  conveniently  calculated  in  British  standard 
measurements  as  follows  :  i  cubic  foot  of  air 

•o8o> 


weighs  -0807  Ib. ;  at  424°  F.  its  weight  becomes 

I-734 
The  loss  of  weight  is  thus  -0761  per  cubic  foot. 

Suppose  a  chimney  of  i  square  foot  in  sectional  area,  and  60 
feet  high,  the  diminution  of  pressure  at  the  base  will  be  for 
424°  F.,  60  x -0761=4-566  Ibs.  per  square  foot,  or  -878  inch  of 
water.  Under  this  pressure,  the  ascensional  velocity  given  by 
I)  K.  Clark  is  as  follows  :— 


74  THE  PRACTICAL  PHYSICS  OF 

_  ~      /      /  T1         \  when  H  =  height  of  chimney, 

^  H(~T~  I  )  T1  =  highest  temperature  on 

absolute  scale, 
T  =  lowest  temperature  on 

absolute  scale. 
In  the  above  case  the  calculation  is  :  — 


v=  --  i\  =8  v/6o(r8  -  i)  =  8  \/48  =56  ft.  per 

second  nearly. 

Taking  for  example  i  kilo,   of   Blanzy  coal,  having  the  com- 
position   carbon   76-5,   disposable  hydrogen   3'!   per  cent.,  the 
combustion  of  that  quantity  of  this  coal  requires  :  — 

Oxygen  ......  2-288  kilos  =1-597  cubic  metres 

Nitrogen    ...  7-660     ,,     =6*098     ,,          „ 

Air  ......  9-948     „     =7-695     „ 

Calling  that  quantity  of  air  7-700  cubic  metres,  the  resulting 
products  of  combustion,  in  escaping  at  200°  C.,  carry  off  890 
calories,  or  nearly  ^  part  of  the  heat  produced  by  the  combus- 
tion of  the  coal. 

The  mechanical  work  necessary  to  supply  a  fire  with  7-700 
cubic  metres  of  air  at  a  pressure  of  a  water  column  of  1  1  milli- 
metres high,  which  corresponds  to  IOTOO  kilos,  per  square 
metre,  will  be  10-100x7-700=77-7,  or,  in  round  numbers,  78 
kilogrammetres.  The  mechanical  equivalent  of  i  calorie  being 
nearly  425  kilogrammetres,  we  thus  find  that  the  heat  dispersed 
into  the  atmosphere  by  the  gases  at  200°  C.  causes  the  dis- 
appearance of  power  equivalent  to  890  calories  x  425  =  378,  250 
kilogrammetres,  in  order  to  produce  a  useful  effect  equal  to  78 
kilogrammetres.  The  relation  of  the  loss  to  the  useful  effect  is 
thus,  theoretically  :  — 


78  i 

To  ascertain  the  practical  relation  of  loss  to  useful  effect,  we 
have  to  allow  for  the  useful  effect  of  steam  engine  and  fan. 
Engines  give  out  only  0*055  Per  cent,  of  the  power  which  is 
represented  by  the  heat  possessed  by  the  steam,   and  the  useful 
effect  of  fans  is  not  more  than  o-io  to  0-20.     The  practical  rela- 
tion which  we  wish  to  establish  will  therefore  be  expressed  by  :  — 
4-849  x  0*0055  __  26-66 
i  i 


THE  MODERN  STEAM  BOILER.  75 

which  amounts  to  saying  that  to  produce  the  movement  of  air 
in  fires  by  the  natural  draught  of  chimneys,  we  spend  26  times 
as  much  heat  as  we  should  need  to  spend  in  order  to  produce 
the  same  effect  by  means  of  steam  engines  and  fans. 

In  this  calculation  only  the  theoretical  quantity  of  air  required 
for  combustion  has  been  assumed,  and  it  is  certain  that  if  a 
larger  quantity  \vere  taken,  the  loss  of  heat  by  chimney  draught 
would  be  much  greater.  Taking  the  example  of  the  Newcastle 
coal,  referred  to  on  page  68,  supplied  with  24  Ibs.  air  per  Ib.  of 
coal,  the  loss  of  heat  with  waste  gases  at  392°  F.  (i.e.,  424°— 32°) 
would  equal  2,323  units  per  Ib.  of  coal.  This,  expressed  in 
units  of  power,  means  that  2,323x772  =  1,793,356  foot-lbs.  are 
expended  in  draught  production.  The  actual  mechanical 
energy  which  would  be  required  to  supply  300  cubic  feet  of  air 
at  a  pressure  of  '878  inch  of  water,  or  4*566  Ibs  per  square  foot, 
amounts  only  to  300x4*566  =  1,370  foot-lbs.,  plus  the  amount 
required  to  overcome  friction,  and  to  make  up  for  loss  of 
efficiency  in  engine  and  fan. 

Mr.  James  Howden  (in  Trans.  Inst.  N.A.,  1884)  compared  the 
expenditure  of  power  as  heat  required  for  natural  draught  in  a 
steamer,  the  boilers  of  which  consume  31,200  Ibs.  of  coal  per 
hour,  520  Ibs.  per  minute  (i.e.,  12,000  I.H.P.  at  2*6  Ibs.  coal  per 
hour  per  I.H.P.),  with  the  power  required  for  mechanical  supply 
of  air  for  boilers  to  provide  the  same  power,  but  consuming 
only  1*6  Ibs.  per  I.H.P.  per  hour  =  19, 200  Ibs.  per  hour  (320  Ibs. 
per  minute).  He  also  supposed  the  air  supply  to  be  15  Ibs.  per 
Ib.  of  coal  consumed  in  both  cases,  but  assumed  that  the  waste 
gases  with  mechanical  supply  would  have  a  temperature  300°  F. 
less  than  those  with  natural  draught.  In  the  first  case,  520  x  15 
=  7,800  Ibs.  \veight  of  air  supplied  per  minute  for  combustion, 
the  weight  of  gaseous  products  of  combustion  being  reckoned 
at  8,281  Ibs.  This  8,281  x  '246  (specific  heat  of  the  waste 
gases)  x  300°  (excess  of  temperature  as  above)  =  6u,i37  heat 
units,  the  expenditure  of  heat  in  this  case.  The  mechanical 

equivalent   of    this   is  6l1'137  x  772  =  i4,296    H.P.     "  This,    of 

33,000 

course,  supposes  the  total  heat  converted  into  work  and 
expressed  in  H.P.  units.  The  actual  value  of  this  expenditure 
of  heat  is  correctly  stated  in  the  ratio  of  the  economy  of  the 
^ngines  and  boilers  which,  at  2*6  per  I.H.P.  per  hour  is  very 


76  THE  PRACTICAL  PHYSICS  OF 

nearly  a  utilisation  of  one-twelfth  of  the  total  heat  of  combustion 
of  coal  of  average  quality  ;  therefore  14,296  -f-  12  =  1,191  is  the 
actual  H.P.  equivalent  of  the  300°  of  heat  lost  in  maintaining  the 
temperature  of  the  funnel  in  the  natural  draught  boilers." 

In  the  other  case,  320  x  15=4,800  Ibs.  of  air  per  minute  would 
be  required  for  combustion.  "  The  volume  required  at  60°,  or 
13  cubic  feet  per  lb.,  is  therefore  4,800  x  13=62,400  cubic  feet. 

"  To  supply  this  volume  per  minute  from  three  fans,  each 
having  discharge  orifices  30  inches  diameter,  or  6^25  square  feet 
area,  giving  a  total  area  of  1875  square  feet,  a  velocity  of  55*46 
feet  per  second  is  required,  as  18*75  x  60  x  55*46  =  62,400.  The 
H.P.  required  to  supply  this  weight  of  air  at  this  velocity  per 

second   is  found  by  the    usual  formula,  ^1.     HereW=48°° 

2g  60 

or  80  Ibs.  air  per  second,   and  -   ^7-^—  =  3,845  foot-lbs.    per 


second,  and     i       =  7  H  p  nearly.      This  7  H.P.  is   the  power 

required  to  supply  the  whole  air  of  combustion  for  12,000 
I.H.P.,  supposing  perfect  efficiency  in  the  fans  and  in  the 
engines  that  drive  them.  Assuming  75  per  cent,  efficiency  in 

the  engines,  and  50  per  cent,  in  the  fans,  we  have  -  -  = 
9*3,  and  9  3  x  ^P—jg^  as  the  gross  H.P.  for  supplying  the 

0 

total  air  of  combustion  to  the    furnaces  mechanically." 

The  relative  economy  in  this  supposed  case  is  as  18*6  is  to 
1,191,  but  of  course  it  would  not  be  in  the  same  proportion  if  a 
smaller  consumption  of  coal  in  the  natural  draught  boilers,  or  a 
less  difference  in  the  final  temperature  of  the  waste  gases,  were 
assumed. 

Rapidity  and  Intensity  of  Combustion.  —  The  increased  rapidity 
and  intensity  of  combustion  are  well  illustrated  now  in  the 
numerous  accounts  of  trials  of  boilers  under  "  natural  draught  " 
and  under  "  forced  draught"  which  have  been  published. 

Admiralty  System.  —  The  late  Mr.  Richard  Sennett,  Engineer- 
in-Chief  of  the  Navy,  gave  the  following  results  of  the  Admiralty 
plan  with  closed  stokeholds,  shown  in  Figs.  38,  39,  40,  in  a 
paper  in  "Transactions  of  the  Institute  of  Naval  Architects  in 
1886." 


THE  MODERN  STEAM  BOILER. 


77 


KICr.      3S. 


FIG.   39. 


FIG.  4O. 


78 


THE  PRACTICAL  PHYSICS  OF 
TABLE  XV. 


I. 

2. 

3- 

4- 

5- 

6. 

7. 

8. 

Ship. 

Date. 

i  Safety  Valves. 

:d  Horse  Power. 

t 

1 

PQ 

0 

Firegrate. 

Indicated 
Horse-Power 
per 

"8 

§flj 

hi 

i 

5 
1 

3 

.y 
•a 

c 

ja 

t/; 
'S 

Area  of 

B| 

P 

0 

1 

Open  Stokeholds. 

It). 

tons. 

"Inflexible" 

1878 

60 

8,484 

756 

829 

10-21 

II'22 

"Colossus" 

1883 

64 

7,492 

594 

645 

11-62 

I2'6l 

"Phaeton" 

1884 

QO 

5,588 

462 

546 

10-23 

I2'I 

Forced  Draught. 

"Howe" 

1885 

90 

11,725 

632 

756 

I5-54 

18-5 

''  Rodney"  (9  boilers) 

1885 

90 

9,544 

474 

567 

16-83 

20'I 

"Mersey" 

1885 

110 

6,628 

306 

399 

16-61 

217 

"Scout" 

1885 

120 

3,370 

174 

207 

16-28 

193 

"  Trafalgar  "  (estimated)    .  .  . 

... 

135 

12,000 

514 

609 

2O'OO 

23-3 

NOTE. — The  weight  of  boiler  given  includes  weight  of  water,  funnel,  uptakes 
fittings,  spare  gear,  etc. 

Mr.  Sennett  remarked  on  these  figures  : — 

By  referring  to  the  seventh  column  of  this  Table,  it  will  be  seen  that 
whilst  in  the  ships  with  natural  draught  only,  about  io£  indicated  horse- 
power was  developed  per  square  foot  of  firegrate,  between  16  and  17  indi- 
cated horse-power  was  obtained  with  moderate  forced  draught,  the  boilers 
being  practically  the  same  in  the  two  cases.  The  steam  blast  ws  used 
throughout  the  trial  of  the  "  Colossus." 

The  grate  area  can  only  be  used  as  a  fair  basis  of  comparison  for  boilers 
similar  in  design  and  construction.  I  have,  therefore ,  in  the  last  column, 
given  the  indicated  horse-power  developed  per  ton  weight  of  boiler,  which  s 
the  more  important  feature,  so  far  as  the  naval  architect  is  concerned,  and  we 
see  from  this  column  that  the  effect  of  the  application  of  forced  draught  has, 
been  to  increase  the  power  obtained  from  a  given  weight  of  boilers  in  the 
proportion  roughly  of  20  to  12,  the  engines  and  boilers  being  of  practically 
the  same  description  in  both  cases. 


THE  MODERN  STEAM  BOILER.  79 

In  the  "  Nile  "  and  "  Trafalgar,"  and  other  warships  now  building,  triple 
expansion  engines  will  be  fitted,  worked  with  steam  of  130  Ib.  to  140  Ib.  pres- 
sure per  square  inch.  From  the  experience  we  have  now  gained  respecting 
the  steam  generating  powers  of  boilers  in  closed  stokeholds  kept  under 
moderate  air  pressure,  and  the  well-known  economical  employment  of  steam 
in  triple-expansion  engines,  we  are  satisfied  that  on  the  full  power  trials  of 
these  vessels  at  least  20  I.H.P.  per  square  foot  of  grate,  and  between  23  and 
24  I.H.P.  per  ton  of  boiler  will  be  realised,  and  this  condition  has  been 
readily  accepted  by  the  engine  contractors  who  have  had  experience  of  the 
working  of  the  system. 

The  two  following  Tables  were  also  given  by  Mr.  Sennett,  and 
furnish  full  details  of  the  machinery  and  of  the  trials  of  the 
various  ships.  From  the  abstract  of  steam  trials,  the  rate  of 
combustion  per  square  foot  of  grate  area  can  be  calculated  in  all 
but  the  second  trial  of  the  "  Rodney,"  and  the  figures  have  been 
added  to  the  Table  as  published  by  Mr.  Sennett.  The  insertion 
of  three  examples  of  vessels  worked  with  open  stokeholds  and 
only  partial  use  of  blast  enables  a  comparison  to  be  made. 


8o 


THE  PRACTICAL  PHYSICS  OF 


"  Trafalgar  " 
proposed. 

d   j       .     | 

*  «  J  •-  li  •£  •-   'i 

•€.5-2^  =  S"     *        v 
£*jh>  S-3'3     "S 

li  [i,  i-a  „  L    *-,.- 

VI 
?! 

filf  si 

j  If  ||t*  t  ^§f§n!U  ?  ?  K- 

~ 

0 

If!  Eii' 

1  S      1   «=       ?    d                       x"7                             - 

1  2       e    gfiw     g     ~  g>8  P,  -,      =  '=•«            5     i?        « 

s 

• 

'§|3          •3f7"^^ 
K  -3    "         "    '        w 

-3    ^            .2      •=    x                =                      1^  0                                                    10 

-  2        •=     ~£                   _;  --^  °             c    °               "^      °          -^ 

£    r           ^;      "    o    ~                   •-=>'?  '^,2    "     '"     —      f*           "         "•         **** 
?    ^                                                 -                                               •_ 

"  Phaeton." 

£  i    ;        ^  *^  o 

jjij,|,s&.|jE,,f:,, 

~3 
I 

0 

! 

j  >TS  of  5 

H«      f*d            §^      J                          « 
|      ^  "*'*"'*      '^            ^ 

O 

«     -3         3  ^  2  ^  .-  " 
.^ 

T3 

§               ^"3            ^?^H       S     '    S 
tj     |-==         §  .5     .S                    | 

"f    1^        1^>    2 

5                             H 

1       ?JX=               o^       ^ 

S, 

O           ^ 

2 

c 

1 

ta  N  s                   .1 

I 

X    • 

fj      =  •=            3  -• 
•=  -     '."^  *j         «'=     *j 

^1     ^'^.^        Id     ^ 

"H 

\     1        J    :t|    :5 

Jlf 

"^.      ...         .         .  c  i>  "i;  '*"    •      •    *-s  *    S         5=-SiJ*:'v 

s    «  :  :  :  :    :    :'=-§l?:  :  g»  •=-&  l§  Ns 

8fe      S          ^--E              =£    o5   i!;    »S3 

ilp!i!ii=li  ij^1!1? 

2     £      J$£x    a  j?3|sr^|   i  i%     |     <:|    f 
i        ?        v-tl     -^             ^"        -J 

1      I     i     I"8!  1        1      1 

THE  MODERN  STEAM  BOILER. 


81 


""'        «  0    f  0 


0       r.  «  -  w 
O         10  ««•  to  ro  N 


.P      - 


•s 


<o  •— 


SI 


82  THE  PRACTICAL  PHYSICS  OF 

Howden's  System. — In  Mr.  Howden's  plan,  which  is  illustrated 
in  Figs.  41  and  42,  as  carried  out  in  the  s.s.  "  New  York  City,"  in 
1884,  the  rate  of  combustion  gave  17-4  I.H.P.  per  square  foot  of 
grate  area  on  a  consumption  of  coal  equal  to  i'337  Ibs.  per 
I.H.P.  hour  in  one  voyage,  and  in  another  voyage  19*6  I.H.P. 
per  square  foot  of  grate  on  a  consumption  of  i'454  Ibs.  per 
I.H.P.  hour  with  inferior  coal.  About  6  I.H.P.  were  required 
for  the  fan  engine.  On  a  special  occasion  the  full  power  was 
obtained  (with  steam  blowing  off  at  the  safety  valve)  by  the  use 
of  only  two  furnaces,  which  result  Mr.  Howden1  reckons  is  equal 
to  30  I.H.P.  per  square  foot  of  grate. 

Air  Heater. — The  air  for  combustion  was  heated  directly  by 
the  waste  gases,  in  the  heater  placed  in  the  uptake,  to  an 
average  of  190°  over  the  temperature  of  the  air  supply  from  the 
stokehold.  Mr.  Howden  assumed  18^  Ibs.  of  air  as  the  quantity 
used  per  Ib.  of  coal,  and  in  that  event  there  were  190  x  i8'5  x 
•238  =  836-57  units  of  heat  recovered  from  the  waste  gases  per 
Ib.  of  coal  consumed.  It  is  supposed  that  the  air  is  further 
heated  by  its  passage  over  a  portion  of  the  boiler  front  and 
through  the  furnace  boxes  or  passages,  on  Mr.  Howden's  plan, 
and  there  is  no  doubt  that  a  small  addition  to  the  temperature 
may  thus  be  gained.  It  could,  however,  scarcely  reach  450° 
as  Mr.  Howden  supposes  it  does,  in  the  case  of  a  boiler  carrying 
steam  of  80  Ibs.  pressure,  because  the  temperature  of  the  steam, 
and  therefore  of  the  boiler  surfaces  not  exposed  to  the  fire  gases, 
could  not  in  such  a  case  be  above  312°  F.  In  the  s.s. 
"  Indiana,"  and  sister  ships,  having  boilers  with  2,338  square 
feet  of  heating  surface  (or  equal  to  1-63  square  foot  per  I.H.P.), 
and  a  total  grate  area  of  56-5  square  feet,  of  which,  however, 
only  50  square  feet  constituted  the  working  area,  the  rate  of 
working  (as  published  by  Mr.  Howden2)  was  22^  I.H.P.  per 
square  foot  of  total  grate  area,  the  temperature  of  the  waste 
gases,  when  leaving  the  air-heating  tubes,  was  from  420°  to 
450°  F.,  and  the  temperature  of  the  heated  air  was  from  190° 
to  230°  F.  Mr.  Howden  estimates  that  the  temperature  of  the 


1  See  "Trans.  Inst.  N.  A.,"  Vols.  for  1884  and  1886,  on  "  Combustion  of  Fuel 
in  Furnaces  of  Steam  Boilers,"  and  "  On  Forced  Combustion  in  Furnaces  of 
Steam  Boilers,"  by  James  Howden. 

2  "  Forced  Combustion  in  Steam  Boilers,"    "  Trans.   Internat.  Engineering 
Congress,  Chicago,"  1894,  vol.  ii.,  paper  xlii. 


THE  MODERN  STEAM  BOILER. 


84 


THE  PRACTICAL  PHYSICS  OF 


air  can  be  further  raised,  by  increased  heating  surface,  to  300° 
or  350°  F.,  and  that  the  average  temperature  of  the  furnaces 
when  working  as  above  would  be  400°  higher  than  it  would  be 
in  the  same  boiler,  burning  the  same  quantity  of  coal,  if  fitted 
with  the  closed  stokehold  system  of  forced  combustion  with  cold 
air.  The  air  in  the  "  Indiana  "  was  supplied  by  a  u  Sturtevant  ' 
fan  of  54  inches  diameter. 


Scale  2  Inch-1  "root 
FIG.  43. 

Closed  Ashpit  System. — The  closed  ashpit  system,  illustrated  in 
Figs.  43  and  44,  has  been  introduced  in  several  forms.  Mr. 
G.  Ferrando's  plan  was  used  in  several  steamers  belonging  to 
Messrs.  Florio  Rubbatino  and  Co.,' of  Genoa,  and  was  found 
satisfactory  for  moderate  rates  of  combustion  at  about  20  Ibs.  of 
fuel  per  square  foot  of  grate  surface.  With  higher  rates  of 
combustion  there  was  a  danger  of  the  flame  being  forced 
through  the  furnace  doors,  on  account  of  the  funnel  being 


THE  MODERN  STEAM 


unable  to  discharge  the  large  volume  of  waste  gases.  An 
improved  method  of  distributing  the  air  was  introduced  in  the 
s.s.  "  Marmora,"  by  Mr.  Fothergill,  with  good  results.1  A  recent 
example  of  the  closed  ashpit  system  was  fitted  by  Mr.  D.  J. 
Dunlop2  in  the  steam  yacht  "  Mira,"  in  which  i  H.P.  was 
obtained  from  1*45  square  feet  of  heating  surface  of  the  boilers, 


and  2i'66  H.P.  per  square  foot  of  grate  surface.  The  total 
heating  surface  was  1,317  square  feet,  and  the  grate  area  42 
square  feet.  The  steam  pressure  was  160  Ibs.  per  square  inch, 
and  the  total  I. H.P.  907,  the  weight  of  machinery  being  at  the 
rate  of  207  Ibs.  per  I. H.P. 

'See  "Trans.   X.E.    Coast  of   Engineers   and  Shipbuilders,   1886,"  Vol.  ii. 
-  Engineering,  i8th  March,  1892,  p.  351. 


86  THE  PRACTICAL  PHYSICS  OF 

Suction  System. — Ellis  &  Eaves'  Plan. — The  use  of  a  fan  for 
exhausting  the  products  of  combustion,  or  producing  a  partial 
vacuum  at  the  base  of  the  funnel,  has  been  introduced  in  the 
plans  of  Ellis  &  Eaves  and  of  Patterson.  This  system  has  been 

called  "Induced,"  but  more  commonly"  Suction"  or  u  Exhaust  " 
draught. 

In  the  case  of  the  former  of  these  plans  illustrated  in  Figs.  45  and 
46,  with  a  grate  of  5ft.  9in.  long,  a  rate  of  combustion  of  30  to  60  Ibs. 
per  square  foot  of  grate  surface  has  been  obtained  in  marine 
boilers  of  the  "  Scotch  "  or  cylindrical  kind  on  land,  and  of  26  to 
31^  Ibs.  per  square  foot  at  sea  in  the  Atlantic  and  Australian 
merchant  services,  "  without  troubles  to  furnaces,  tube  plates, 
tube  ends,  fans  and  fan  engines,  accompanied  by  an  appreciable 
economy  compared  with  the  boilers  of  the  same  size,  with  plain 
tubes  working  with  natural  draught  at  half  the  rate  of  combus- 
tion." In  the  Ellis  &  Eaves'  plan  the  use  of  an  exhaust  fan  is 
combined  with  that  of  the  "  Serve  "  or  internally  ribbed  tube, 
generally  with  a  specially  shaped  retarder  for  the  gases  added 
inside  the  ribs,  and  with  air-heating  tubes  in  the  waste  gases 
carried  to  a  greater  extent  than  in  other  plans. 

Table  XVIII.1  gives  the  principal  dimensions  and  results 
of  working  in  the  case  of  five  steamers  fitted  with  this 
plan. 

Mr.  Howden  has  advanced2  some  considerations  to  prove  that 
a  considerable  increase  of  power  is  required  to  drive  fans  on 
this  system,  as  compared  with  his  own  plan  of  delivering  the 
air  for  combustion  at  a  slight  pressure  into  the  furnace  and  ash- 
pit, but  it  is  not  our  province  to  enter  into  this  argument. 
There  is  probably  more  power  required  on  account  of  the  larger 
volume  of  products  to  be  dealt  with  in  given  time,  and  probably 
also  because  a  greater  amount  of  vacuum  is  required  at  the 
smoke-box  end,  on  the  suction  plan,  than  of  pressure  at  the 
furnace  end  of  the  system,  on  the  forcing  plan.  On  the  other 
hand  it  may  be  the  case  that  with  the  suction  plan  a  greater 
velocity  of  movement  of  hot  gases  over  the  heating  surfaces  is 
obtained,  and  this,  if  carefully  utilised,  may  cause  a  better  result 

1  See  Paper   by  J.   D.  Ellis.     Trans.   Inst.  N.  A.      1893.      Also   Paper  by 
F.  Gross.     Trans.  Inst.  N.  A.     1894. 

2  Proceedings  of  the  International  Engineering  Congress  at  Chicago.    1893. 
Vol  ii.,  paper  xlii. 


THE  MODERN  STEAM  BOILER. 


:    I 


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88 


THE  PRACTICAL  PHYSICS  OF 


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Length  of  grate  ... 
Total  heat-distributiiij 
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THE  MODERN  STEAM  BOILER. 


89 


in  transference  of  heat  from  these  gases  to  the  water.'  This, 
however,  cannot  be  dealt  with  here. 

In  Patterson's  plan1  (Fig.  47)  there  is  the  addition  of  a  spray  of 
water  which  is  injected^into  the  fan  for  the  purpose  of  keeping 
it  cool,  to  prevent  danger  of  warping,  and  to  protect  the 
mechanism  generally.  Beyond  the  results  given  by  Mr.  Paul  iti 
his  paper,  however,  there  does  not  seem  to  have  been  much 
done  as  yet  with  this  plan. 

Mr.  Paul  has  recorded  a  consumption  of  coal  in  a  return- 
tubular  boiler  at  Levenford  Works,  Dumbarton,  equal  to  60  Ibs. 
per  square  foot  of  grate  per  hour,  with  an  evaporation  of  i5lbs.  of 
water  per  square  foot  of  heating  surface  in  the  same  time,  and 


FIG.   47. 

this  is  a  very  good  result.  It  seems,  however,  to  have  been  sur- 
passed in  the  case  of  some  of  the  Niclausse  boilers  in  vessels  of 
the  French  navy,  in  which  the  consumption  of  80  Ibs.  per  square 
foot  of  grate  surface  per  hour  has  been  recorded.2 

Tliomycrofl  Boiler. — The  Table,  at  p.  552,  Chap.  IX.,  gives 
some  results  of  trials  of  Thornycroft's  water  -  tube  boiler, 
with  natural  draught  and  with  moderate  air  pressure  in  closed 
stokeholds,  taken  from  Professor  Kennedy's  report,  which  accom- 
panied Mr.  Thornycroft's  paper3  on  this  subject.  The  follow- 
ing details  are  abstracted  from  the  report  referred  to  : — 

1  See  "  On  Suction  Draught,"  by  Matthew  Paul,  Trans.  Inst.  Eng.  and  Ship- 
builders in  Scotland.     Vol.  xl. 

2  See  Eiigiucciiit",  Jan.   i.,  1897,.  p.  n.     "  Memoires  et  Compte  Rendu  des 
travaux  cle  la  Soc.  des  Ingen.  Civils  de  France."     Jan.,  1898.     pp.  54-69. 

3  Min.  Proc.  Inst.  C.E.,  Vol.  xcix.     1890. 


THE  PRACTICAL  PHYSICS  OF 
TABLE  XIX. 


A. 

D. 

c. 

B. 

E. 

Atmospheric  pressure      

f  14-80     ibs 
(  per.  sq.  in 

}  14-55  Ibs. 

14-80  Ibs. 

14-84  Ibs.       14-45  Ibs. 

Boiler  pressure      

f  186-0     Ibs 
\  per  sq.  in 

}    181-80 

171-20  Ibs. 

149-40  Ibs.      180-5  Ibs. 

Air  pressure  in  stokehold  above 
atmosphere     

I       O'OO 

O'OO 

0-27  in. 

0-49  in. 

2-00  ins. 

Air    temperature    in    stokehold 
above  atmosphere    

} 

69.3°  Fah. 

71-4°  F. 

60-3°  F. 

62-1°  F. 

Coal  burnt  per  hour        

334-0  Ibs. 

203-3  Ibs. 

559-0  Ibs. 

894-0  Ibs. 

1,751-0  Ibs. 

Area  of  fire  grate  

30  sq.  ft. 

26-2  sq.  ft. 

30  sq.  ft. 

30  sq.  ft. 

26-2  sq.  ft. 

Coal  burnt  per  sq.  ft.  of  fire  grate 
per  hour          

j-    iriolbs. 

774  Ibs. 

i8'6o  Ibs. 

29-80  Ibs. 

66-80  Ibs. 

Feed  temperature  

78-4°  F. 

76-3°  F. 

78-00  F. 

83-8°  F. 

111-2°  F. 

Water  evaporated  per  Ib.  fuel 

—  * 

1  1  '22  Ibs. 

10-48  Ibs. 

10-20  Ibs. 

8-89  Ibs. 

Equivalent  evaporation  from  and 
at  212°  Faht  

} 

13-40  Ibs.. 

12-48  Ibs. 

12-00  Ibs. 

10-29  m- 

Temperature  of  gases  in  chimney 

474°  F. 

421°  F. 

540°  F. 

610°  F. 

777°  F. 

Air  pressure  in  chimney  

O'OO 

O'OO 

+  0-03  in. 

+  0-12  in. 

-f  0-40  in. 

Total  heating  surface      

1,837  sq.  ft. 

1,837  sq.  ft. 

1,837  sq.  ft. 

1,837  sq.  ft. 

i,  837  sq.ft. 

Ratio  of  heating  surface  to  grate 

,61-2 

70-1 

61-2. 

61-2 

70-1 

Water    evaporated    per    sq.    ft. 

i 

heating  surface  per  hour    ... 

1-24  Ibs. 

3-20  Ibs. 

4-70  Ibs. 

8-50  Ibs. 

Mean  rate  of  heat  transmission 
per    sq.  ft.   heating    surface 

1       — 

f  23-8  heat 
[     units. 

\  6ro  heat 
(     units. 

89  heat 
units. 

158  heat 
units. 

per  hour 

*  Efficiency  of  boiler      

— 

86-8  % 

to-4% 

78-2  % 

66-6  # 

Lbs.  coal  per  I.H.P.  per  hour    ... 

2'220  Ibs. 

2-280  Ibs. 

1-981  Ibs. 

i  -990  Ibs. 

2-260  Ibs. 

*  The  boiler  efficiency  is  expressed  in  terms  of  the  ratio  between  the  actual  evaporation  and 
that  theoretically  due  to  the  fuel  calculated  from  analysis  in  the  usual  way. 

Locomotive  Results. — In  the  case  of  locomotive  engines,  with 
steam  blast  pipe  in  the  chimney  producing  a  powerful  induced 
draught,  a  vacuum  of  seven  to  eighteen  inches  water  column  has, 
according  to  Mr.  J.  A.  F.  Aspinall,1  been  produced  at  the  chimney 
end,  three  to  seven  inches  in  the  smoke-box,  and  one  to  three  inches 
over  the  brick  arch  in  the  fire-box.  The  mean  of  several  trials 
registered  a  coal  consumption  of  60  Ibs.  per  square  foot  of  grate 
surface  per  hour,  with  a  vacuum  of  three  inches  in  the  smoke- 
box,  which  corresponds  with  about  one  inch  in  the  fire-box. 
An  express  locomotive,  it  has  been  said,  burns,  on  an  average, 
100  Ibs.  of  coal  per  square  foot  per  hour.  In  general,  the  rate 
of  combustion  with  forced  draught  seems  to  vary  directly  as  the 


1  "  Draught  in  Locomotive  Boilers,"  by  J.  A.  F.  Aspinall,  Proc.  Inst.  Mech. 
Engineers.     1893. 


THE  MODERN  STEAM  BOILER.  91 

square  root  of  the  air  gauge  height,  whether  plenum  or  vacuum. 
Mr.  M.  Paul  remarks,  in  the  paper  already  referred  to,  that 
applying  this  rule  to  Mr.  AspinalFs  results,  "  it  is  found  that 
with  a  vacuum  of  three  inches  in  the  fire-box,  the  coal  will  be 
burned  at  the  rate  of  60  x  v/3  =  io5lbs.  per  square  foot  of  grate 
per  hour,  and  this  is  confirmed  by  various  authorities  as  a 
common  performance  in  locomotive  boilers."  Mr.  Paul  adds, 
"  With  forced  draught,  a  plenum  of  three  inches  is  required  for 
a  coal  consumption  of  6olbs.  per  square  foot  of  grate  per  hour, 
and  for  io5lbs.  per  square  foot  of  grate  a  plenum  of  nine  inches 
would  be  required,  but  this  has  not  yet  been  reached." 


FIG.   48. 

Air  Pressure. — Regarding  the  amount  of  air  pressure  to  be 
permitted  in  marine  boilers,  Mr.  A.  F.  Yarrow1  made  the  follow- 
ing remarks  :  "In  the  passage  of  the  air  from  the  stokehold  to 
the  funnel,  the  greater  part  of  the  resistance  to  be  overcome  in 
most  cases  is  due  to  forcing  the  air  through  the  tubes  ;  conse- 
quently, if  a  contractor  be  limited  to  a  given  amount  of  air 
pressure,  the  only  means  he  has  to  meet  this  condition  without 
extra  weight  is  by  augmenting  the  diameter  of  the  tubes,  or 
reducing  their  length,  thus  producing  rigidity,  which  I  have 
already  pointed  out  is  bad.  Because  a  certain  boiler  does  not 
stand  a  given  air  pressure  without  the  tubes  leaking  only  proves 
that  this  air  pressure  is  too  much  for  that  boiler,  but  does  not 
prove  that  it  is  too  much  for  every  boiler,  especially  in  view  of 

1  Trans.  Inst.  N.A.,  vol.  xxxii.,  p.  105. 


92  THE  PRACTICAL  PHYSICS  OF 

the  fact  that  locomotives  are  working  all  over  the  world  at  air 
pressures  varying  from  three  to  eight  inches. 

"  Fig.  48  shows  the  vacuum  in  the  smoke-box  of  a  Midland 
engine.  This  has  been  kindly  given  me  by  Mr.  Johnson.  In 
confirmation  of  the  high  air  pressure  used  on  locomotives,  I 
quote  the  following  statement  of  a  locomotive  superintendent 
of  one  of  our  local  lines  :  '  We  do  not  consider,  from  our  ex- 
periments, that  a  vacuum  of  eight  inches  in  a  smoke-box  is  any- 
thing exceptional,  but  should  expect  it  when  working  full  power, 
either  going  up  a  bank  or  drawing  a  heavy  train  on  a  level.  In 
addition  to  the  vacuum  in  the  smoke  box  we  register  a  pressure 
.of  air  in  the  front  of  the  ash  pan,  due  to  the  speed  of  the 
train,  of  two  inches  of  water,  making  a  total  pressure  of  ten 
inches.'  With  these  facts  before  us  there  ought  to  be  no 
condition  imposed  upon  the  marine  engineer  limiting  the  air 
pressure." 

Kemp's  Feed  Heater. — Before  passing  on  to  consider  possible 
methods  of  improving  the  combustion  in  boilers,  it  is  necessary 
to  refer  to  the  results  obtained  by  the  late  Mr.  E.  Kemp  in  the 
application  of  feed-water  heaters,  wrought  by  means  of  heat  in 
the  waste  gases,  to  marine  boilers.  He  first  commenced  with  a 
heater  (Fig.  49)  having  a  small  proportion  (about  3^  per  cent.) 
of  heating  surface  relatively  to  that  of  the  boiler,  but  latterly  had 
heaters  (Figs.  50,  .51)  having  over  twice  the  boiler-heating  surface, 
a.  distinct  gain  in  temperature  of  the  feed-water  accompanying 
these  additions  to  the  surface  of  the  heaters. 

The  system  was  tried  with  natural  chimney  draught  (Fig.  49) 
and  with  forced  draught  on  both  the  suction  (Fig.  50)  and  the 
closed  ashpit  (Fig.  51)  plans.  The  following  Tables  and  Figs, 
give  the  particulars  of  the  various  vessels  fitted  and  the  re- 
sulting temperatures  of  feed  water  and  of  waste  gases. 
Additional  details  will  be  found  in  Mr.  Kemp's  paper, ""  On  Com- 
pound Marine  Boilers."  ] 

All  the  vessels  named  in  Table  i  had  the  arrangement  of 
apparatus  showrn  in  Fig.  49,  with,  ho\vever,  an  increase  of  surface 
in  each  succeeding  case.  The  s.s.  "  Bleville  "  was  fitted  with  the 
arrangement  shown  in  Fig.  50,  and  the  s.s.  "  Caloric '  with  that 
shown  in  Fig.  51. 

1  Trans.  Inst.  Eng.  and  Shipbuilders,  Vol.  xxxii.,  p.  201. 


THE  MODERN  STEAM  BOILER. 


53 


TABLE  XX. 


PARTICULARS  OF  MARINE  BOILERS 

AND  FEED  HEATERS. 

NAME     OF 
STEAMER 

WHEN 
BUILT 

HEATING  SIH) 

•FACE'«BOUR 

HI9SURR 
"FEEDHT" 

FEED  SURF? 

TOBOIL'SIK 

TEMP? 
RAISED 

FIKUSES 
UTILISED 

BOILER 
PRESSURE 

"PLANTYN" 

1879 

FEET 

3580 

FEET 
13? 

l™26-6 

ABOUT 

15° 

ABOVI 

\yf 

LBS. 

80 

"PIETERDECOfflliCK 

1881 

5697 

216 

1«2H 

15° 

w° 

80 

"SORRINTO" 
"MARSALA" 

1881 
1882 

3992 

1*8 

Ito26^ 

16° 

U? 

80 

'CLAN  CAMERON" 
'CLAN  CAMPBELL" 
"CLAN  FORBES" 
"CLANOGILVIE" 

1882 

$018 

20? 

M9-68 

20° 

150° 

85 

"CLAN  GRANT" 

1883 

5899 

397 

l™^.85 

25° 

1^0° 

85 

"TAORMINA" 

I88f 

3992 

W 

lT»9-6^ 

V° 

180° 

80 

PARTICULARS  OF  COMPOUND 
HIGH  AND  LOW  TEMPERATURE  MARINE  BOILERS. 

NAME   or  (WHEN 

STEAMER      BUILT 

HTSSURF" 
"H.T.BOILEI1 

HTSSURF" 

•LT.BOILER 

LT.SURFAO 
TMSUHPi 

TEMP? 
RAISED 

FISECASC 
UTUJSEIl 

BOILER 
PRESSURE 

"BLEVILLE1886 

1768 

3392 

l-91«l 

150° 

<wo° 

160 

"CALORIC"  [1887 

1613 

5505 

2-17"! 

WOT 

«o9 

160 

TABLE  XXI. 


94 


THE    PRACTICAL   PHYSICS   OF 


WATER  FROM 
ENGINE 


FIG,  49A. 


THE    MODERN    STEAM    BOILER. 


95 


96 


THE    PRACTICAL    PHYSICS  OF 


THE  MODERN  STEAM  BOILER. 


97 


Comparison  of  Air  and  Feed-heaters. — In  discussing  Mr.  Kemp's 
results,  Mr.  Howden  instituted  a  comparison  between  the  feed- 
heater  of  the  "  Caloric  "  and  the  air  heater  which  he  had  intro- 
duced into  the  "  New  York  City,"  in  order  to  prove  that  the 
heat-absorbing  power  of  air  is  superior  to  that  of  water.  The 
same  view  had  already  been  expressed  by  Mr.  Howden  in  his 


WATER  FROM 
ENGIN 


FIG.  51. 

paper  on  "  Forced  Combustion  in  Furnaces  of  Steam  Boilers  " 
(Trans.  I.N.A.,  1886),  in  which  he  criticised  some  remarks  made 
by  Mr.  J.  T.  Milton  in  his  previous  paper  "  On  the  Efficiency  of 
Marine  Boilers "  (Trans.  I.N.A.,  1885).  Mr.  Howden  said  ' 
"  the  boiler  of  the  '  New  York  City '  had  a  total  heating  surface 
of  1,597  square  feet,  that  of  the  '  Caloric '  being  1,613  square 
feet.  Taking  the  coal  consumed  in  the  *  Caloric  '  as  9^  tons 

1  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland,  Vol.  xxxii.,  p.  213. 


98  THE  PRACTICAL  PHYSICS  OF 

per  day,  as  stated  by  Mr.  Kemp,  or  863^  Ibs.  per  hour,  and  if  for 
simplicity  of  calculation,  the  evaporation  of  water  was  taken  at 
lolbs.  per  Ib.  of  coal,  there  were  therefore  8,633  Ibs.  of  feed 
water  passing  through  the  heaters  per  hour.  The  dimensions  of 
these  feed  heaters,  as  given  by  Mr.  Kemp,  after  deducting  the 
space  occupied  by  the  118  tubes  in  each  heating  vessel,  left  a 
capacity  for  5,256  Ibs.  of  water  in  each,  and  as  8,633  Ibs.  of  feed 
water  were  supplied  per  hour,  the  time  taken  in  passing  through 
one  feed-heating  vessel  was  therefore  36^  minutes,  and  2  hours 
26  minutes  in  passing  through  the  four  heating  vessels.  In  the 
boiler  of  the  '  New  York  City '  the  air-heating  chamber,  through 
which  the  whole  air  for  combustion  passed,  had  a  total  heating 
surface  of  225  square  feet,  and  the  capacity  of  the  chamber  was 
i6'8  cubic  feet.  The  coal  consumed  on  the  trial,  at  which  he 
was  present  and  ascertained  the  results,  \vas  1,030  Ibs.  per  hour; 
and  as  20  Ibs.  of  air  were  used  for  combustion  per  Ib.  of  coal 
consumed,  the  total  weight  of  air  passing  through  the  heater  per 
hour  was  20,600  Ibs.  The  temperature  of  the  air  on  entering 
the  heater  was  70°,  and  on  leaving  250°,  so  that  the  air  was 
raised  180°  in  temperature  in  passing  through  the  heater.  The 
volume  of  air  entering  the  heater  was  accordingly  13-4  cubic  feet 
per  Ib.,  and  on  leaving  17-86  cubic  feet  per  Ib.  As  20,600  Ibs.  of 
air  passed  through  the  heater  per  hour,  575  Ibs.,  or  86-25  cubic 
feet  passed  through  per  second  ;  and  as  the  total  capacity  of  the 
air-heating  chamber  was  16*8  cubic  feet,  it  followed  that  the  air- 
heating  chamber  was  replenished  5*13  times  every  second,  so 
that  each  particle  of  air  was  less  than  |  of  a  second  in  contact 
with  the  heating  surface  in  passing  through  the  heater.  This 
gave,  so  far,  the  means  of  comparing  the  relative  absorbent 
powers  of  air  and  water.  In  the  '  Caloric '  there  were  8,633  Ibs. 
of  water  raised  140°  in  temperature  per  hour  by  contact  with 
3,505  square  feet  of  heating  surface,  but  each  particle  of  water 
had  been  in  contact  with  or  under  the  effect  of  the  heating  sur- 
face for  2  hours  26  minutes,  while  in  the  air-heater  of  the  '  New 
York  City'  20,600  Ibs.  of  air  per  hour  had  been  raised  180°  by 
contact  with  only  225  square  feet  of  heating  surface,  but  where 
each  particle  had  also  only  been  in  contact  with  the  heating  sur- 
face '194  of  a  second.  Putting  aside,  meanwhile,  the  time  the 
air  had  been  in  the  one  case  and  the  water  in  the  other,  under 
the  heating  power  in  their  respective  apparatus,  and  taking 


THE  MODERN  STEAM     BOILER.  99 

the  values  of  the  specific  heat  of  the  8,633  Ibs.  of  water 
raised  140°  per  hour  in  the  '  Caloric/  and  of  the  20,600  Ibs.  of 
air  raised  180°  per  hour  in  the  '  New  York  City/  their  relative 
values  are  water  i,  and  air  '7178.  The  air  was,  however,  in- 
creased in  temperature  by  contact  with  only  T'^  of  the  heating 
surface  with  which  the  water  had  been  in  contact,  so  that  the 
air  had  absorbed  ii'4  times  more  heat  in  the  case  of  the  '  New 
York  City  '  than  the  water  had  in  the  '  Caloric '  for  equal  areas 
of  heating  surface." 

Such  a  comparison  is,  however,  quite  illusory,  because  of  the 
enormous  difference  in  the  rates  of  movement  of  the  particles, 
these  being,  according  to  Mr.  Howden's  figures,  as  i  for  the 
water  to  about  40,000  for  the  air.  Mr.  Howden  evidently  felt 
that  it  was  not  wholly  satisfactory,  as  he  added,  that  to  test "  the 
superior  heat-absorbent  powers  of  air  over  water  "  fairly,  "  equal 
weights  of  each  should  pass  over  equal  surfaces  under  the  same 
temperature  in  equal  times."  But  even  this  would  be  misleading. 

Heat  Absorbing  Powers  of  Air  and  Water. — The  specific  heats 
of  water  and  air  for  equal  weights,  as  determined  by  Regnault, 
are  water  roo,  air  0*2374,  so  that  the  quantity  of  heat  which 
would  raise  i  Ib.  of  air  i  degree,  would  raise  i  Ib.  of  water  only 
o-2374°,  or,  in  other  words,  water  requires  about  four  times  the 
quantity  of  heat  to  raise  its  temperature  that  is  required  by  the 
same  weight  of  air.  Nevertheless,  it  does  not  follow  that  air  is 
necessarily  raised  in  temperature  more  rapidly  than  water.  Both 
are  bad  conductors,  but  still  air  is  undoubtedly  a  much  worse 
conductor  of  heat  than  still  water.  As  in  the  case  of  all  fluids, 
except  perhaps  mercury,  heat  is  conducted  through  them  almost 
wholly  by  convection,  and  freedom  of  movement  is  vital  to  con- 
vection. Where  a  comparison  between  the  heat-absorbing 
powers  of  two  fluids  can  be  made  is  when  both  are  outwardly 
quiescent,  for  then  the  speed  of  the  action  is  dependent  cm  the 
spontaneous  or  unassisted  movement  of  their  particles.1  If  the 
view  that  air  is  superior  to  water  as  a  heat-absorbent  were 
correct,  air,  instead  of  water,  should  be  used  as  the  circulating 
medium  in  surface  condensers.  But  the  largely  increased  surface 
required  in  air  condensers,  as  compared  with  water  condensers, 
bears  witness  to  the  relative  values  of  the  two  as  heat  absorbers. 

1  See  also  C.  Wye  Williams  on  "  The  Combustion  of  Coal,  etc.,"  pp.  164,  165. 

E2 


TOO  THE  PRACTICAL  PHYSICS  OF 

In  his  experiments  with  air  condensers,  the  late  Mr.  Thos. 
Craddock  found  that  hot  water  in  a  metal  tube,  when  immersed 
in  still  air,  took  twenty-five  minutes  to  cool  from  180°  F.  to 
100°  F.,  whilst  in  still  water  the  same  amount  of  cooling  took 
place  in  one  minute.  When  the  tube  was  moved  in  the  water  at 
the  rate  of  3  feet  per  second,  the  rate  of  cooling  was  doubled,  or 
half  a  minute  sufficed  for  the  loss  of  80°.  When,  however,  the 
tube  was  moved  at  the  rate  of  59  feet  per  second  in  air,  the  rate 
of  cooling  was  12  times  that  of  still  air,  but  was  even  then  only 
about  half  the  rate  in  still  water. 

In  such  vessels  as  the  feed-heaters  there  is  no  large  volume  of 
water  whose  particles  are  free  to  move  and  set  up  convection 
currents  in  the  mass,  and  consequently  rapid  movement  from  an 
extraneous  source  must  be  provided  to  take  the  place  of  natural 
convection.  In  the  case  of  Mr.  Kemp's  feed-heaters  this  motion 
of  the  water  \vas  undoubtedly  too  slow  for  an  economic  result, 
but  if  the  suitable  rate  of  movement  for  maximum  result  with 
water  were  attained  in  them,  it  is  probable  that  for  an  equal  result, 
air  would  require  to  have  a  velocity  at  least  200  or  300  times 
as  great.  In  the  article  "  Heat  "  in  u  Encyclopaedia  Britannica," 
Qth  edition,  Sir  Wm.  Thomson  gave  the  thermal  conductivity  of 
iron  at  80  times,  and  that  of  copper  at  500  times,  that  of  water  ; 
and  compared  with  air,  he  said  that  the  conductivity  of  iron  was 
3,500  times,  and  that  of  copper  20,000  times,  that  of  air — so  that 
the  thermal  conductivity  of  water  is  over  40  times  that  of  air. 

Improved  Methods  of  Combustion. — In  order  to  effect  improve- 
ment in  the  combustion  department  of  marine  and  other  boilers, 
attention  must  be  given  to  the  means  for  diminishing  labour,  for 
utilising  the  lower  qualities  of  fuel,  and  for  increasing  the 
intensity  of  combustion.  The  conditions  of  work  on  board  ship 
militate  against  the  adoption  of  mechanical  stoking  arrangements 
such  as  are  applied  to  the  ordinary  furnace  grates  on  land. 
Moreover,  there  are  strong  reasons  why  such  grates  should  be 
abolished.  Putting  aside  mechanical  stokers,  we  have  the  choice 
of  firing  with  gas,  firing  with  coal  dust,  or  using  external  firing 
chambers  with  mechanical  feeding.  For  gas-firing,1  the  intro- 

1  For  gas-firing  with  boilers  on  land,  see  D.  K.  Clark,  "The  Steam  Engine," 
Vol.  i.,  p.  346  ;  Mills  and  Rowan  "  On  Fuel,  etc."  ;  Groves  and  Thorp's 
Technology,  Vol.  i.,  pp.  535-582  ;  "  Gas-Fired  Boilers,"  Trans.  Mining  Inst. 
of  Scotland,  Vol.  xi.,  1889. 


THE  MODERN  STEAM  BOILER.  101 

duction  of  gas  producers  on  board  ship  is  beset  with  difficulties, 
and  the  additional  weight  which  they  import  into  the  machinery 
department  is  itself  a  strong  argument  against  them.  Apart 
from  the  use  of  gas  producers,  there  is  little  chance  of  obtaining 
economical  firing  with  gas,  unless  a  really  efficient  method  of 
quickly  gasifying  crude  oils  were  worked  out.  The  use  of 
liquid  fuel,  by  means  of  the  ordinary  arrangements  for  burning 
it  in  the  form  of  spray,  seems  to  be  hopeless  of  any  satisfactory 
prospect.  As  so  used,  twice  the  calorific  value  of  good  coal 
is  scarcely  ever  reached,  whilst  the  comparative  cost  of  the 
fuel,  at  even  that  rate,  quickly  causes  any  monetary  benefit  to 
vanish. 

Dust  Fuel. — The  use  of  powdered  coal  is  more  promising, 
especially  in  the  forms  introduced  by  Wegener,  Schwartzkopf, 
Ruhl,  De  Camp,  or  Friedeberg,  in  Germany,  which  are  modifica- 
tions of  the  plan  originally  tried  by  Crampton.  These  plans  are 
illustrated  in  the  published  Transactions  of  the  Federated 
Institute  of  Mining  Engineers,  Vol.  xi.,  PI.  18,  those  of  De  Camp 
and  Friedeberg  being  combined  with  an  air-blast  produced  by 
a  fan.  A  full  description  of  them  will  be  found  in  a  paper  by 
Mr.  Bryan  Donkin,  Member  of  the  Institute  of  Civil  Engineers, 
in  the  Transactions  of  the  Federated  Institute  of  Mining 
Engineers,  Vol.  xi.,  p.  321.  Refer  also  to  Engineering  New: 
(New  York),  Vol.  xlv.,  pp.  452,  453.  They  undoubtedly  providi, 
methods  of  complete  and  rapid  combustion,  without  much  exces  j 
of  air,  and  without  cooling  of  the  boiler  by  frequent  opening  ot 
furnace  doors,  but  have  drawbacks  due  to  the  necessity  for  the 
presence  of  coal-crushing  machinery  to  grind  the  coal  as  it  is 
used — as  coal  dust  cannot,  with  safety  and  economy,  be  stored  in 
bulk  in  the  coal  bunkers  of  steamships — and  to  the  fact  that  all 
the  ash  of  the  coal  is  blown  into  the  boiler  furnace  or  casing, 
from  which  its  removal  must  be  attended  with  very  great 
difficulty. 

External  Firing  Cha tubers. — The  use  of  external  firing  chambers 
has  so  much  to  recommend  it  that  the  only  wonder  is  that  they 
have  not  long  ago  been  adopted.  It  is  possible  to  use  small  coal 
or  slack  in  them,  and  the  fuel  can  be  fed  continuously  by 
mechanical  means  of  the  simplest  kind.  The  air,  as  well  as  the 
coal,  is  mechanically  supplied,  and  there  is  no  necessity  for 
opening  charging  doors,  so  that  the  great  causes  of  fluctuations  in 


102 


THE  PRACTICAL  PHYSICS  OF 


temperature  at  the  boiler  surfaces  are  abolished,  with  the  heavy 
labour  of  hand  stoking. 


FIG.   52. 


KIG.   53. 


A  plan  which  was  proposed  by  the  author  in  1876  is  shown 
in    Figs.   52,    53.      This    combustion   chamber  was    somewhat 


THE  MODERN  STEAM  BOILER. 


103 


similar  in  design  to  one  invented  by  Herr  C.  Wittenstrom,  of 
Stockholm,  for  the  reheating  furnaces  of  forges,  and  which 
acted  fairly  well  when  properly  supplied  with  fuel. 

Another  plan,  proposed  by  Captain  Hamilton  Geary  in  1887,  i§ 
shown  in  Fig.  54  (A  and  B).  This  furnace  was  devised  principally 
for  using  anthracite  in  steam  boilers,  and  succeeded  well  in  the 
trials  carried  out  in  1877  by  Captain  Geary. 


B 


FIG.  54  (A  AND  B). 

Although  the  advantages  of  an  external  firing-chamber  for 
land  boilers,1  as  regards  completeness  of  combustion  and  absence 
of  smoke,  had  long  been  known,  nothing  was  done  with  these 
plans,  and  the  system  has  still  to  be  advocated  as  something  new 
and  as  yet  foreign  to  general  practice,  but  certain  in  time  to 
become  necessary  to  the  proper  working  of  boilers. 

Combustion  under  Increased  Pressure. — The  further  step  which 
must  ultimately  be  taken  in  this  department  of  the  subject  is 

1  See  Mills  and  Rowan  "  On  Fuel,  etc.,"  pp.  513,  575-5^3- 


104  THE  PRACTICAL  PHYSICS  OF 

that  of  conducting  the  combustion  under  considerable  pressure. 
The  pressures  hitherto  reached  with  the  systems  of  forced  or 
accelerated  draught  in  use  do  not  amount  to  more  than  3  inches 
of  water  column  in  marine  boilers  and  8  to  10  inches  in 
locomotive  boilers,  but  these  are  a  long  way  short  of  what  will 
be  required  in  the  system  here  advocated.  The  rationale  of 
combustion  under  increased  pressure  should  be  readily  under- 
stood. 

It  was  proved  years  ago,  by  Poisson  and  Laplace,  that  the 
specific  heat  of  a  gas  maintained  at  constant  volume  is  less  than 
that  of  the  same  gas  maintained  at  constant  pressure,  the  differ- 
ence between  the  two  being  caused  by  the  quantity  of  heat 
which  is  rendered  latent  by  the  expansion  of  the  gas.  In  other 
words,  if  a  given  weight  of  any  gas  is  allowed  to  expand  freely 
whilst  it  is  being  heated,  a  greater  amount  of  heat  is  necessary 
to  raise  its  temperature  a  given  number  of  degrees  than  would 
be  required  for  the  same  rise  of  temperature  where  the  gas  is 
maintained  at  a  constant  volume.  It  is  clearly  seen,  that  if  a 
given  volume  of  a  gas  which  has  been  compressed  or  heated 
under  any  given  pressure  is  allowed  to  expand  to  a  lower 
pressure,  its  temperature  will  fall,  and  that  a  corresponding  rise 
of  temperature  must  accompany  the  opposite  action. 

The  variation  of  the  temperature  of  air  under  these  conditions 
has  been  expressed  by  following  formula  : — 

(/P\  0.29\ 
(/  + 461-2)  x^J      | -461-2 

where 
/  =  the  temperature  of  the  air  in  degrees  F.  at  the  pressure  p 

T  —  P 

n  jj  j)  i)  r- 

The  pressures  P  and  p  are  measured  above  a  vacuum  and  may 
be  expressed  either  in  atmospheres,  Ibs.  per  square  inch,  or  any 
convenient  unit  of  measurement.  The  0-29th  power  of  the 

p 
fraction    —  may  be  obtained  by  the  use  of   logarithms.      The 

specific  heat  of  air  when  maintained  at  constant  volume  (i.e., 
with  pressure  increasing)  is  0*169  >  and  when  maintained  at 
constant  pressure  (i.e.,  with  volume  free  to  increase),  0*238,  as 
compared  with  water  as  ro.  Thus  i  Ib.  of  air  in  expanding  to 
the  extent  corresponding  to  a  rise  of  temperature  of  i°  F., 
absorbs,  or  renders  latent,  o'238—-o-i69=o-o69  of  a  unit  of  heat. 


THE  MODERN  STEAM  BOILER.  105 

When  air  is  compressed,  a  sensible  rise  of  temperature  is 
noticed,  which  is  due  to  the  heat  which  has  been  employed 
in  maintaining  it  in  an  expanded  state  becoming  sensible.  "  In 
carrying  on  combustion  under  pressure  the  products  are  not  first 
allowed  to  expand  and  then  become  heated  by  compression,  but 
they  are  prevented  from  expanding  as  they  would  under  ordinary 
circumstances,  and,  as  far  as  effects  go,  the  results  are  the  same 
as  if  they  were  compressed.  In  other  words,  the  temperature  to 
be  expected  in  a  furnace  working  at  a  pressure  of  two  atmos- 
pheres will  be  the  same  as  if  the  products  obtained  by  combustion 
under  ordinary  atmospheric  pressure  were,  before  becoming 
cooled,  compressed  to  one  half  their  volume."  This  rise  of 
temperature  may  be  calculated  by  the  formula  already  given, 
taking  for  instance  the  temperature  of  the  products  resulting 
from  combustion  under  atmospheric  pressure  at  2700°  F.  above 
the  normal  temperature  of  the  air  and  fuel,  which  may  be 
assumed  at  60°  F.  The  temperature  of  the  products  will  in  that 
case  be  2760°  F.,  and  assuming,  as  we  may  without  sensible 
error,  that  the  formula  for  air  is  applicable  to  these  gaseous 
products  of  combustion,  the  effect  of  conducting  the  combustion 
at  a  pressure  of  two  atmospheres  will  be  : — 

(/^v   0.29\ 
(2760  +  461-2)  x  (-  J         -  461-2 

=  (3221-2  x  1-222)  —  461*2  =  3475*1° 

or  a  temperature  715°  higher  than  that  obtained  from  combustion 
carried  on  at  atmospheric  pressure. 

By  increasing  the  pressure  to  three  atmospheres,  a  similar 
calculation  will  show  that  a  further  increase  of  temperature 
amounting  to  493°  may  be  expected. 

A  corroboration  of  the  main  facts  here  indicated  will  be  found 
in  the  results  of  Regnault's  investigations  of  the  specific  heats  of 
gases,  a  resume  of  which  is  given,  under  "  Heat,"  in  Watts' 
"  Dictionary  of  Chemistry,"  Vol.  iii.,  pp.  24-52  ;  81-136. 

The  effect  of  pressure  in  increasing  the  temperature  of 
combustion  has  been  illustrated  in  numerous  experiments  by 
Frankland,1  who  found  that  many  flames  which  are  non- 
luminous  at  ordinary  atmospheric  pressure  become  luminous 

1  See  "  Experimental  Researches  "  ;  also  Jour.  Chem.  Soc.,  Vol.  xvii.  (1864), 
PP-  52-55  ;  Bl"it.  Assocn.  Reports,  Vol.  xxxviii.,  p.  37  ;  Proc.  Royal  Soc.,  Vol. 
xvi.  (1868)  ;  Phil.  Mag.,  Vol.  xxxvi.  (1868),  pp.  309-311. 


io6  THE  PRACTICAL  PHYSICS  OF 

when  exposed  to  considerable  pressure.  So  general  was  this 
result  found  to  be  that  Frankland  deduced  from  it  the  principle 
that  the  luminosity  of  flames  depends  chiefly  upon  the  density  of 
the  vapours  formed  by  the  chemical  action  of  combustion,  the 
temperature  being  affected  in  proportion.  Further  illustration 
of  the  subject  is  found  in  the  high-pressure  furnaces  introduced 
experimentally  in  1869  by  Sir  (then  Mr.)  Henry  Bessemer, 
accounts  of  which  will  be  found  in  Engineering,  Vol.  viii.  (1869), 
pp.  197,  261,  and  in  Proceedings  of  the  Cleveland  Institution  of 
Engineers,  9th  February,  1871,  in  a  paper  by  Mr.  W.  H.  Maw, 
from  which  some  of  the  foregoing  facts  and  arguments  have 
been  borrowed.  Theoretically  a  limit  is  imposed  upon  the 
realisation  of  high  temperatures  of  combustion  by  dissociation, 
but  where  heat  is  rapidly  and  continuously  abstracted  from 
flame,  as  is  the  case  in  steam  boiler  furnaces,  it  is  very  unlikely 
that  the  dissociation  temperature  of  carbon  dioxide  could  be 
maintained,  if  ever  reached.  Moreover,  Bunsen's  researches 
long  ago  showed  that  wrhere  oxygen  is  mixed  with  an  inert  gas, 
such  as  nitrogen,  as  is  the  case  in  atmospheric  air,  even  where  no 
excess  of  air  is  employed  in  combustion,  such  dilution  lowers  the 
possible  temperature  of  combustion  (as  compared  with  what  is 
possible  with  pure  oxygen),  so  that  a  larger  proportion  of  the 
combustible  gas  can  enter  into  combination  with  oxygen  on 
account  of  the  action  of  dissociation  being  delayed.  Bunsen 
showed  also,  that  by  successive  undulations  of  temperature  over 
a  comparatively  short  range,  successive  quantities  of  gas  enter 
into  combustion,  producing  flame,  and  that  thus  a  temperature 
very  little  short  of  the  dissociation  point  can  be  maintained.  On 
this  subject  there  are  some  particulars  in  Mills  and  Rowan 
"  On  Fuel  and  its  Applications."  (Vol.  i.  of  Groves  and 
Thorp's  Chemical  Technology,  pp.  366-368.  See  also  "  On 
Flame,"  Journal  Society  Chemical  Industry,  3oth  March,  1889.) 
In  applying  the  method  of  combustion  under  high  pressure 
to  water-tube  boilers  it  will,  of  course,  be  necessary  to  construct 
pressure-proof  casings,  but  this  does  not  offer  any  serious 
difficulty.  In  fact,  this  casing  might  form  a  feed-water  heater. 
It  would  be  desirable,  also,  to  have  an  index  of  the  amount  of 
pressure  existing  in  the  combustion  chamber  from  time  to  time, 

1  See  also  Engineering,  Vol.  xi.,  p.  181,  etc. 


THE  MODERN  STEAM  BOILER. 


107 


and  this  could  be  readily  afforded  by  the  use  of  such  a  gauge  as 
the  ingenious  one  applied  by  Mr.  Bessemer  (See  Fig.  55)  to  his 
high-pressure  furnaces,  or  some  modification  of  it. 

It  is  evident  from  these  considerations  that  the  temperature 
produced  in  furnaces,  and  to  which  boiler  surfaces  are  exposed, 
does  not  depend  primarily  upon  the 
weight  of  air  used  per  pound  of  fuel 
consumed,  even  when  that  combustion 
is  judiciously  effected,  but  upon  the 
quantity  of  fuel  brought  under  com- 
bustion in  a  given  time  and  space — the 
greater  the  quantity  consumed  the 
higher  being  the  temperature  —  and 
upon  the  pressure  under  which  the 
combustion  takes  place. 

It  follows  from  this  that  the  proper 
basis  for  regulation  of  the  area  of  uptake 
and  Hues  is  not  the  grate  area,  but  is 
rather  the  weight  of  fuel  which  is  burnt 
in  given  time,  combined  with  the  velocity 
with  which  the  gases  are  made  to  travel 
in  these  passages.  In  fact,  the  main 
unit  for  the  comparison  or  proportion- 
ing of  boiler  measurements  is  evidently 
the  fuel  ;  the  heating  surface  being 
required  in  proportion  to  the  number 
of  heat  units  to  be  dealt  with  (derived 
from  the  combustion  of  the  fuel  and 
transmitted  to  the  water),  and  the 
quantity  of  water  being  also  in  strict 
relation  to  that  number.  Further,  the 
size  of  furnace  or  combustion  chamber, 
and  the  quantity  of  air  required,  are  directly  dependent  upon 
the  weight  of  fuel  to  be  burnt. 

Progress  is  even  now  being  made  in  the  direction  indicated  in 
this  chapter.  Since  it  was  written  the  following  account  of 
experiments  in  America  has  appeared  in  Trans.  American  Soc. 
of  Naval  Architects,  a  summary  having  been  published  in  a 
daily  paper  (the  Glasgow  Herald,  of  October  iQth,  1899).  It 
records  no  mere  trial  of  a  mechanical  stoker  applied  to  the 


FIG.   55. 


io8  THE  PRACTICAL  PHYSICS  OF 

ordinary  grate  of  a  marine  boiler.  Such  an  application  has  been 
made  more  than  once  in  past  times.  It  is  clear  from  the 
account  given  that  we  have  here  the  record  of  a  serious  step 
towards  the  introduction  of  a  separate  firing  chamber,  with 
mechanically  fed  fuel  and  possibly  a  higher  degree  of  forced 
combustion  than  the  ordinary  one,  and  it  is  the  possession  of 
these  features  which  gives  such  interest  to  the  experiments 
recorded. 

Considerable  importance  attaches  to  a  series  of  tests  made  by  the  United 
States  naval  authorities  with  water-tube  boilers  using  mechanical  stokers,  as  it 
is  recognised  that  automatic  firing  would  confer  enormous  advantages  in  the 
direction  of  economy  of  fuel  of  poor  quality,  regularity  of  stoking,  freedom 
from  smoke,  and  reduction  of  stokehold  staff.  The  results,  which  are  very 
elaborate,  are  most  promising.  The  vessel,  a  large  steamer  of  10,155  tons 
displacement,  has  two  of  Babcock  and  Wilcox  water-tube  boilers,  supplying 
steam  of  about  250  Ibs.  pressure  to  quadruple  expansion  engines  of  about  1,600 
indicated  horse-power.  The  boilers  have  5,000  square  feet  of  heating  surface, 
the  weight  being  65  tons,  excluding  water,  which  weighs  15  tons.  Three 
mechanical  underfed  stokers  are  fitted  to  each  boiler.  Small  coal  thrown  into 
a  hopper  is  continually  fed  by  a  conveyor  screw  into  a  central  magazine,  and 
in  this  it  is  gradually  forced  upwards,  overflowing  the  tuyere  blocks,  through 
which  air  is  supplied  by  a  blower.  The  coal  is  gradually  heated  as  it  is  forced 
up  in  the  magazine,  and  thus  the  volatile  gases  are  released  and  are  burned  by 
the  air  issuing  from  the  inside  of  the  tuyere  blocks.  A  sort  of  coke  is  at  the 
same  time  furnished  to  the  dead  grates  at  the  sides  of  the  stoker,  and  the  air 
for  the  combustion  of  this  is  supplied  by  the  openings  on  the  outside  of  the 
tuyere  blocks.  At  the  side  of  each  stoker  is  a  door  for  cleaning  the  grate,  etc., 
and  this  could  be  utilised  for  ordinary  stoking  if  the  mechanism  went  wrong. 
No  air  is  admitted  except  through  the  tuyeres.  The  weight  of  each  stoker 
complete  is  3,500  Ibs.  Inferior  coal  was  used — a  cheap  grade  of  slack,  the 
calorific  value  of  a  test  sample  having  been  11,790  British  thermal  units  per 
Ib.  when  dry.  The  steam  and  water  were  measured  for  both  main  and 
auxiliary  engines,  and  it  was  found  that  the  six  stokers  used  138-6  Ibs.  of  steam 
per  hour,  equal  to  4-29  per  cent,  of  the  total  steam  generated  ;  but  when  the 
blower  exhaust  was  passed  through  the  feed  heater  the  cost  was  only  r68  per 
cent,  of  the  total.  The  stoker  worked  satisfactorily  in  all  tests— six  trials  each 
of  six  hours  were  made — and  it  was  found  that  the  main  engines  used  on  an 
average  about  14-4  Ibs.  of  steam  per  horse-power  hour,  and  the  auxiliaries 
2'5  Ibs.  per  hour  per  horsepower  of  the  main  engines,  the  latter  equal  to  about 
14  per  cent,  of  the  total.  The  coal  consumption  for  the  main  engines  varied 
between  1-63  and  r88  Ibs.,  and  for  all  machinery  1-9  to  2*20  Ibs.  The  water 
evaporation  averaged  about  n  Ibs.  per  Ib.  of  coal  from  and  at  212  degrees. 
These  results,  in  view  of  the  quality  of  coal,  are  most  satisfactory,  and  the 
United  States  naval  authorities  have  been  impressed  by  the  results  ;  but  it  is 
significant  that  they  state  that  the  steam  consumption  of  the  quadruple  engine 
is  not  less  than  with  triple-expansion. 


CHAPTER    IV. 

TRANSMISSION  OF  HEAT. 

The  Steam  Boiler  a  Heat-Engine. — The  successful  transmission  of 
heat  is  the  true  solution  of  the  greatest  problem  of  boiler  design. 
Several  years  ago  it  was  shown  that  the  proper  light  in  which  a 
boiler  should  be  regarded  is  that  of  a  heat-engine,  to  which  the 
reasoning  used  in  the  case  of  all  other  examples  can  be  applied. 
"The  apparatus  by  means  of  which  the  potential  energy  of  fuel, 
with  respect  to  oxygen,  is  converted  into  the  potential  energy  of 
steam,  we  call  a  steam  boiler,  and  although  it  has  neither 
cylinder  nor  piston,  crank  nor  fly-wheel,  I  claim  for  it,"  said 
Mr.  Anderson,1  "  that  it  is  a  veritable  heat-engine,  because  it 
transmits  the  undulations  and  vibrations  caused  by  the  energy 
of  chemical  combination  in  the  fuel,  to  the  water  in  the  boiler ; 
these  motions  expend  themselves  in  overcoming  the  liquid 
cohesion  of  the  water  and  imparting  to  its  molecules  that  vigour 
of  motion  which  converts  them  into  the  molecules  of  a  gas 
which,  impinging  on  the  surfaces  which  confine  it  and  form  the 
steam  space,  declare  their  presence  and  energy  in  the  shape  of 
pressure  and  temperature.  A  steam  pumping-engine  which 
furnishes  water  under  high  pressure  to  raise  loads  by  means  of 
hydraulic  cranes,  is  not  more  truly  a  heat-engine  than  is  a 
simple  boiler,  for  the  latter  converts  the  latent  energy  of  fuel 
nto  the  latent  energy  of  steam,  just  as  the  pumping  engine 
converts  the  latent  energy  of  steam-  into  the  latent  energy  of 
the  pumped-up  accumulator  or  the  hoisted  weight."  This  is 
undoubtedly  the  true  point  of  view  from  which  to  regard  steam 
boilers  in  principle,  and  the  application  of  this  view  reaches 
a  good  deal  farther  than  any  method  of  estimating  the  heat 
efficiency  of  boilers  which  has  as  yet  been  employed. 

Heat  Efficiency  of  Boilers. — The  efficiency  of  a  boiler  is  at  present 
derived  from  the  calculated  evaporative  power  of  the  fuel,  divided 

1  "  On  the  Generation  of  Steam  and  Thcrmorlynamic  Problems  Involved." 
Min.  Fro.  Inst.  C.E.,  1883-84. 


no  THE  PRACTICAL  PHYSICS  OF 

into  the  actual  evaporation  obtained  in  Ibs.  of  water  per  Ib.  of 
fuel  consumed  in  the  boiler,  or  in  other  words,  the  percentage 
of  the  calculated  heat  value  in  the  fuel  utilised  in  evaporating 
water  into  steam  is  made  the  basis  of  comparison  of  the  heat 
efficiency  of  boilers.  Mr.  J.  G.  Hudson  (in  the  Engineer,  Vol.  70, 
page  449)  takes  the  final  efficiency  E  of  a  boiler,  /.<?.,  the  propor- 
tion which  the  heat  utilised  in  raising  steam  bears  to  the  full 
calorific  value  of  the  fuel  expended,  as  the  product  of  the 
separate  efficiencies  of  the  successive  stages  of  the  process. 
Thus  :— 

Ej=the  efficiency  of  the  combustion  = 

the  heat  developed 


the  calorific  value  of  the  fuel 

the  heat  absorbed 

k  =the  efficiency  or  the  absorption=      —r= — : — — -: : r- 

the  heat  developed 

^  ....      .  the  heat  utilised 

E,=the  efficiency  of  the  utilisation  = 

the  heat  absorbed 

then  E1xE2xE3=E 

and  remarks  that  "  under  exceptionally  favourable  conditions 
the  numerical  values  might  be  Ex='96,  E2='93,  E3='97,  making 
E  =  '866  ;  whilst  more  commonly  they  would  be  £^-90, 
E2=75,  E3='95,  making  £  =  '641,  and  much  lower  values 
are  met  with."  He  proposes  to  estimate  E2  by  taking  the 
weight  and  specific  heat  of  the  waste  gases  and  their  temperature 
in  excess  of  that  of  the  fuel  and  air  as  supplied  to  the  boiler, 
and  deducting  that  from  the  total  heat  developed.  But  this  tells 
us  nothing  about  the  amount  of  heating  surface  which  has  been 
required  in  the  boiler  in  the  production  of  this  result,  and  conse- 
quently (as  the  same  rate  of  evaporation  might  be  obtained  from 
boilers  having  very  different  amounts  of  heating  surface)  it  is 
not  a  good  basis  for  comparison  of  various  boilers.  To  obtain 
that  we  would  require  to  have  a  proportion  between  the  number 
of  heat  units  which  can,  theoretically,  be  transmitted  per  unit  of 
heating  surface  per  unit  of  time,  and  the  number  actually  trans- 
mitted in  the  case  of  any  boiler,  either  per  unit  of  surface  or 
through  the  total  heating  surface  in  the  boiler.  The  calculated 
heat  value  of  fuel  is  by  no  means  so  exact  or  reliable  an  amount  as 
is  the  number  of  heat  units  required  to  evaporate  a  given  weight 
of  water  in  given  time,  so  that  if  we  know  the  evaporative  duty  of 


THE  MODERN  STEAM  BOILER.  in 

a  boiler  and  its  total  area  of  hen '.ing  surface,  we  can  at  once  test 
its  efficiency  in  terms  of  heat  transmitted,  that  is,  consistently 
with  the  view  of  the  boiler  as  a  heat-engine.  It  will,  of  course, 
be  necessary  to  agree  upon  a  standard,  or  the  maximum  amount 
of  heat  transmission  which  is  theoretically  possible  per  unit  of 
surface,  but  this  should  not  be  difficult  to  do. 

Carnot's  Law. — The  reasoning  applied  to  heat-engines  is 
founded  on  the  law  or  principle  announced  first  by  Carnot,1  that 
the  ratio  of  the  greatest  possible  work  performed  by  a  heat- 
engine  to  the  whole  heat  expended  is  a  function  of  the  two 
limits  of  temperature  between  which  the  engine  works,  and  not 
of  the  nature  of  the  substance  employed.  It  has  been  pointed 
out  by  several  writers  on  physics  that  the  greatest  range  of  tem- 
perature possible  is  that  which  is  measured  on  the  absolute  scale 
between  the  highest  temperature  at  the  commencement  of  the 
cycle  of  operations  and  absolute  zero,  and  the  fraction  of  this 
difference  or  range  which  can  be  utilised  is  the  ratio  which  the 
range  of  temperature  through  which  the  substance  is  working 
bears  to  the  absolute  temperature  at  the  commencement  of  the 
action. 

If  W  =  the  greatest  amount  of  effect  to  be  expected,  T  and  t 
=  the  absolute  temperatures  at  beginning  and  end  of  the  cycle, 
and  H  =  the  total  quantity  of  heat  potential  in  the  substance  at 
the  higher  temperature  T,  then  the  application  of  Carnot's  law 
gives  us  the  expression 


Illustration  of  Cantot's  Law. — Mr.  W.  Anderson  (in  his  lecture 
"  On  the  Generation  of  Steam,"  etc.)  gave  the  following  graphic 
illustration  of  this  doctrine  :  "  Fig.  56  represents  a  hillside  rising 
from  the  sea.  Some  distance  up  there  is  a  lake,  L,  fed  by  streams 
coming  down  from  a  still  higher  level.  Lower  down  the  slope 
is  the  millpond,  P,  the  tail  race  from  wrhich  falls  into  the  sea.  At 
the  millpond  is  established  a  factory,  the  turbine  driving  which 
is  supplied  with  \vater  by  a  pipe  descending  from  the  lake  L. 
Datum  is  the  mean  sea-level,  the  level  of  the  lake  is  T,  and  of  the 
millpond  /.  Q  is  the  weight  of  water  falling  through  the  turbine 

1  Reflexions  sur  la  Puissance  Motrice  de  Feu,  Paris,  1824.  Sir  William 
Thomson,  "  Account  of  Carnot's  Theory,"  Proc.  Roy.  Soc.  Edin.,  Vol.  xvi. 
(1849). 


112 


THE  PRACTICAL  PHYSICS  OF 


per  minute.  The  mean  sea-level  is  the  lowest  level  to  which  the 
water  can  possibly  fall,  hence  its  greatest  potential  energy,  that 
of  its  position  in  the  lake,  is  QT=H.  The  water  is  working 
between  the  absolute  levels  T  and  /  ;  hence,  according  to  Carnot, 
the  maximum  effect  W  to  be  expected  is 

/T 

W=H( 

but  H=Q  T,  therefore  W=Q  T  (~? 

and  W=Q  (T  — /) 

that  is  to  say,  the  greatest  amount  of  work  which  can  be  expected 
is  found  by  multiplying  the  weight  of  water  into  the  clear  fall, 


T-A 
~T~J 


FIG.    56. 

which  is,  of  course,  self-evident.  Now,  how  can  the  quantity  of 
work  to  be  got  out  of  a  given  weight  of  water  be  increased  with- 
out in  any  way  improving  the  efficiency  of  the  turbine  ?  In  two 
ways  : — 

1.  By  collecting  the  water  higher  up  the   mountain  and  by 
that  means  increasing  T. 

2.  By  placing  the  turbine  lower  dowrn,  nearer   the    sea,  and 
by  that  means  reducing  /. 

"  Now,  the  sea-level  corresponds  to  the  absolute  zero  of  tem- 
perature and  the  heights  T  and  t  to  the  maximum  and 
minimum  temperatures  between  which  the  substance  is  working  ; 
therefore,  similarly,  the  way  to  increase  the  efficiency  of  a  heat- 
engine,  such  as  a  boiler,  is  to  raise  the  temperature  of  the 


THE  MODERN  STEAM  BOILER.  113 

furnace  to  the  utmost,  and  to  reduce  the  heat  of  the  waste 
gases  to  the  lowest  possible  point." 

Methods  of  Increasing  Range  of  Temperature. — We  have  seen  in 
Chapter  III  how  the  temperature  of  combustion  can  be  not  only 
brought  to,  but  also  sustained  at,  the  highest  possible  point,  and, 
putting  aside  for  the  moment  the  question  of  the  use  of 
economisers  and  air  heaters,  the  more  complete  the  transmission 
of  the  heat  to  the  water  in  the  boiler  can  be  made,  the  less  will 
be  the  quantity  of  heat  which  can  escape  in  the  waste  gases.  Of 
course,  the  temperature  due  to*  the  pressure  of  steam  employed 
fixes  a  limit  to  the  temperature  of  the  escaping  gases  and 
therefore  to  this  transmission,  as  far  as  the  boiler  proper  is  con- 
cerned, and  it  is  at  this  point  that  the  use  of  auxiliary  apparatus 
comes  in,  so  that  a  further  amount  of  heat  may  be  extracted 
from  the  waste  gases  or  products  of  combustion. 

As  regards  the  transmission  of  heat,  it  is  not  necessary  to 
discuss  the  refinements  of  the  theory  of  the  action  described  by 
Fourier  (in  his  "  Theorie  analytique  de  la  Chaleur"),1  Poisson 
(in  his  "  Theorie  mathematique  de  la  Chaleur "),  Clerk 
Maxwell  (in  his  "  Theory  of  Heat "),  and  Lord  Kelvin  (in  the 
article  "  Heat  "  in  the  "  Encyclopaedia  Britannica,"  9th  Edition)  ; 
we  are  more  concerned  here  with  its  practical  possibilities. 
Since  the  days  of  Sir  Isaac  Newton  .it  has  been  known  that, 
considering  merely  the  metal  medium,  the  rate  of  transmission 
is  directly  proportional  to  the  difference  of  temperature  between 
the  two  surfaces.  This  Newtonian  principle  was,  in  1818, 
attacked  by  Dulong  and  Petit,  who  concluded,  from  a  series  of 
experiments  on  cooling  in  vacuo  and  in  the  atmosphere,  that 
heat  transmission  took  place  more  rapidly  at  higher  temperature 
differences  than  at  lower.  The  conclusion  of  these  experi- 
menters has,  however,  been  corrected  by  subsequent  investigation, 
and  the  general  accuracy  of  Newton's  view  has  been  maintained. 
In  fact,  the  early  experiments  of  Dulong  and  Petit,  Narr, 
Colding,  and  others,  as  well  as  many  more  recent  ones  on  this 
and  other  allied  subjects,  seem  to  deserve  the  pithy  remark 
of  one  writer,  who  says  :  "  Whatever  there  can  be  said  for 
or  against  the  deductions  of  the  experiments  referred  to,  they 

1  There  is  an  English  translation  of  Fourier's  work,  by  Freeman,  published 
in  1^79  at  Cambridge  University  Press,  i  vol.  8vo. 


ii4  THE  PRACTICAL  PHYSICS  OF 

all  involve  the  same  error,  viz.,  that  of  deducing  a  law 
of  universal  application  from  too  small  a  series  of  experi- 
ments, in  which  factors  having  an  undoubted  influence  were 
omitted." 

Great  differences  have  been  found  in  general  practice,  the 
average  drift  of  which  has  been  in  the  opposite  direction  to  that 
of  Dulong  and  Petit's  conclusion,  for,  as  we  shall  see,  in  the 
transmission  of  heat  for  evaporation,  better  results  have  been,  so 
far,  obtained  with  a  difference  of  temperature  of  about  100°  F. 
than  with  one  of  1000°  and  upwards.  The  results  obtained 
with  steam  boilers,  and  in  various  experiments  connected  with 
them,  have  in  fact  induced  some  engineers  rather  hastily  to 
form  the  conclusion  that  the  rule  for  boilers  is  that  the  rate  of 
transmission  of  heat  from  the  hot  gases*  to  the  water,  across  the 
boiler  plates  or  metal  of  the  tubes,  is  proportional  to  the  square 
of  the  difference  of  temperatures,  in  all  cases.  That  boiler 
practice,  however,  has  been  far  from  embracing  all  the  elements 
which  can  contribute  to  the  best  results  possible,  and  the  most 
of  the  experiments  alluded  to  have  been  of  a  very  partial  and 
incomplete  kind,  except  perhaps  as  regards  the  special  form  of 
apparatus  experimented  with  in  one  or  two  instances.  Some 
factors,  such  as  for  instance  the  absolutely  essential  and  indeed 
commanding  one  of  the  effect  of  movement,  have  been  either 
wholly  or  partially  ignored  in  them. 

Conduction  of  Heat. — The  rule  for  the  rate  of  conduction  of 
heat  by  the  metal  itself  seems  to  have  been  well  ascertained.  It 
is  thus  expressed  by  Professor  Clerk  Maxwell  ("  Theory  of  Heat," 
P-  234)  :— 

H  =  —  —  (T-S) 

H  being  =  the  whole  heat  conducted  in  time  /. 

a  b    ,,      =    ,,    area  of  the  plate. 

c        „      =    ,,     thickness  of  the  plate. 

T  —  S  being  =  the  difference  of  temperature  which  causes  the 

flow  and 
k  being  =  the  specific  thermal  conductivity  of  the  substance.   ' 

"  It  appears  therefore/'  Professor  Clerk  Maxwell  says,  "that  the 
heat  conducted  is  directly  proportional  to  the  area  of  the  plate, 
to  the  time,  to  the  difference  of  temperature,  and  to  the  con- 
ductivity, and  inversely  proportional  to  the  thickness  of  the 


THE  MODERN  STEAM  BOILER.  115 

plate."     As  to  the  dimensions  of  k,  the  specific  thermal  con- 
ductivity, he  adds,  "  From  the  equation  we  find 

k=  c  H 

a  b  t  (T— S) 

"  Hence  if  [L]  be  the  unit  of  length,  [T]  the  unit  of  time,  [H] 
the  unit  of  heat,  and  [0]  the  unit  of  temperature,  the  dimen- 
sions of  k  will  be 

[H] 
[LTfl] 

"  If  heat  is  measured  in  thermal  units,  such  that  each  thermal 
unit  is  capable  of  raising  unit  mass  of  a  standard  substance 
through  one  degree  of  temperature,  the  dimensions  of  H  are 


[M  0]  and  those  of  k  will  be 


'   Ml" 

LLTJ 


Many  similar  expressions  of  this  law  or  principle  of  heat 
conduction  have  been  given,  in  which  other  symbols  have  been 
used,  and  perhaps  the  most  convenient  one  is  the  following  :  — 

=  ks  '—  T 


Where  Q  is  the  quantity  of  heat  which  passes  through  a  layer  of 
the  substance  of  thickness  £,  and  area  s,  in  time  T,  when  its  two 
surfaces  are  kept  at  the  constant  temperatures  /  and  /'  for  a 
sufficient  time  to  establish  an  even  flow,  k  stands  for  the  co- 
efficient of  conductivity. 

Coefficient  of  Conductivity.  —  This  coefficient  of  conductivity 
has  been  investigated  by  several  experimenters,  who  have  used 
principally  three  different  methods  or  processes,  the  most  direct 
of  which  is  said  to  have  been  that  employed  by  Peclet.1  This 
consisted  in  u  measuring  the  time  required  for  a  given  quantity 
of  heat  to  pass  through  plates  of  different  materials  of  definite 
thickness,  the  two  surfaces  being  maintained  at  known  constant 
temperatures  by  keeping  the  two  sides  of  the  plate  bathed  with 
water." 

Peel  el's  Experiments.  —  Peclet  at  first  used  a  form  of  apparatus 
in  which  steam  was  employed  as  the  source  of  heat  on  one  side 
of  a  plate,  whilst  water  was  in  contact  with  the  other  surface, 
over  which  it  was  moved  by  means  of  a  rotating  agitator.  He 

!Ann.  Chem.  Phys  [3],  ii.  107  and  "  Traite  de  la  Chaleur,"  etc.  Liege, 
1844,  chap  viii.  (3rd  edn.) 


n6  THE  PRACTICAL  PHYSICS  OF 

noticed  in  all  the  experiments  with  this  apparatus  that  the  quan- 
tity of  heat  transmitted  was  sensibly  affected  by  the  speed  of 
rotation  of  the  agitator,  increasing  or  diminishing  in  proportion 
to  that  speed,  but  the  limit  of  speed  of  movement  possible  with 
the  apparatus  was  too  small.  He  therefore  constructed  a  new 
apparatus,  with  the  means  of  giving  a  greater  movement  to  the 
water,  which  he  now  used  on  both  surfaces  of  the  plates,  as  he 
thought  that  a  film  of  condensed  steam  in  the  previous  apparatus 
probably  interfered  with  the  correctness  of  the  results  or  with 
the  rate  of  transmission.  This  new  apparatus  is  shown  in  Figs. 
56A,  57,  and  58  in  which  Fig.  56A  is  a  vertical  section  of  the  whole 
apparatus,  Fig.  57  is  a  plan,  and  Fig.  58  a  section  (on  an  enlarged 
scale)  of  the  bottom  of  the  upper  cylinder  or  vase,  showing  the 
plate  experimented  with  at  EF.  The  water  wras  agitated  on  the 
upper  surface  of  the  plate  by  the  vertical  paddle,  and  on  the 
under  side  by  the  horizontal  wheel  RS,  which  was  moved  by 
means  of  the  handle  X.  By  means  of  this  apparatus  Peclet  was 
able  to  renew  the  liquid  in  contact  with  the  surfaces  of  the 
metal  plate  1,600  times  a  minute,  and  he  obtained  for  lead  plates 
the  coefficient  3*84  in  kilogram,  water  degrees  for  one  square 
metre  of  surface,  one  millimetre  of  thickness,  and  one  second  of 
time,  per  i°  C.  difference  of  temperature. 

Taking,  then,  the  numbers  given  by  Despretz1  for  the  relative 
conductivity  of  the  different  metals,  Peclet  gave  the  following 
Table  of  coefficients  of  absolute  conductivity. 

TABLE  XXII. 

Gold       ...  ...  ...  ...  21-28 

Platinum  ...  ...  ...  20-95 

Silver     ...  ...  ...  ...  2071 

Copper  ...  ...  ...  ...  19-11 

Iron        ...  ...  ...  ...  7-95 

Zinc        774 

Lead       ...  ...  ...  3*84 

Wiedeniann  and  Franz's  Results. — There  seems,  however,  to 
be  some  reason  to  doubt  this  order,  as  later  results  given  by 

1  These  are  given  by  D.  K.  Clark  in  "  A  Manual  of  Rules,  Tables,  and  Data," 
p.  331,  Table  107. 


THE  MODERN  STEAM  BOILER. 


117 


FIG.   57. 


n8 


THE  PRACTICAL  PHYSICS  OF 


Wiedemann  and  Franz1  (Pogg.  Annal.  Ixxxix.  497),  which  are 
said  to  have  been  most  carefully  ascertained,  present  the  relative 
conductivity  of  the  metals  in  a  different  order  of  value.  Their 
results  are  given  in  the  following  Table,  the  coefficients  of  abso- 
lute conductivity  being  calculated  from  these  numbers  on  the 
basis  of  Peclet's  result  for  lead,  and  expressed  in  gramme  water 
degrees,  per  minute,  per  centimetre  thickness,  per  square  centi- 
metre of  surface  : — 

TABLE  XXIII. 

CONDUCTIVITY    OF   METALS. 


Relative. 

Absolute. 

Silver       

IOO 

45-2 

Copper 

73*6 

3V4 

Gold 

24'O 

Brass 

23-1 

I0'4 

Zinc 

IQ'O 

8-6 

Tin 

6-^5 

Iron         

n-9 

538 

Lead        

8-4 

3-84 

Platinum...         ...         ...         ... 

8'5 

379 

German  Silver  ... 

6-3 

2-85 

Bismuth  

r8 

0-81 

Both  Neumann2  and  Angstrom3  have  also  investigated  the 
conductivity  of  metals,  and  have  given  the  following  results 
which  have  been  reduced  to  expressions  of  absolute  conductivity 
according  to  the  same  units  at  temperature  /°. 

In  the  column  A  the  numbers  refer  to  i  gram,  degree  Cent,  as 
the  unit  of  heat,  i  centimetre  as  unit  of  length,  and  i  minute  as 
the  unit  of  time.  In  column  B  the  units  are  i  kilogram,  degree, 
i  millimetre,  i  square  metre,  i  second. 

-1  See  also  Watts'  Diet,  of  Chemistry,  Vol.  v.,  p.  71. 

2  Ann.  Chem.  Phys.  [3]  Ixvi.,  185. 

3  Pogg.  Ann.  cxiv.  527;    cxviii.  429,  see  also  Watts'  Diet,  of  Chemistry, 
Article  "  Heat,"  Vol.  vi.,  p.  693. 


THE  MODERN  STEAM  BOILER. 

TABLE  XXIV. 


119 


Angstrom. 

Neumann. 

_          A           

A.                         1                           H. 

A. 

Copper 

j  6f63  (r  —  O-OO2I4  /) 

(58-94(1—  o-oo  1519  /) 

102-7  (i—  0-003  567/1  ) 

98-23(1—  0-002532/)  [ 

66-48 

110-75 

Zinc 

... 

18-43 

30-70 

Brass 

18-12 

30-19 

Iron              — 

11-927  (I—  0-002^74  t) 

19-88  (i  —  0-00479  0 

9-82 

16-37 

German  Silver 

... 

6-57 

10-94 

Lead 

(A)  2-30      (B)  3-84                      Peclet. 

Mr.  D.  K.  Clark1  calculated  from  Peclet's  Table,  (XXII.,  on 
page  1 1 6)  into  English  measures,  the  quantities  of  heat  transmitted 
from  water  to  water  through  plates  of  metals  i  inch  thick,  per 
square  foot,  for  i°  F.  difference  of  temperature  between  the  two 
faces,  per  hour. 

His  figures  are  given  in  the  following  Table. 

TABLE  XXV. 


Substances. 

Quantity  of  Heat  in  Units. 

Gold 

62O 

Platinum 

604 

Silver 

596 

Copper 

555 

Iron 

225 

Zinc 

225 

Tin 

177 

Lead 

112 

Mr.  Clark  quotes  the  following  formula  from  Peclet  to  express 
1  A  Manual  of  Rules,  Tables,  Data,  etc.,  3rd  edn.,  page  460. 


120  THE  PRACTICAL  PHYSICS  OF 

the  law  of  transmission  of  heat  through  metals  (or  other  sub- 
stances) :  — 


in  which  /  and  tl  are  the  temperatures  of  the  surfaces,  C  the 
quantity  of  heat  transmitted  per  hour  for  one  degree  difference 
of  temperature  through  i  unit  of  thickness,  and  E  is  the  thick- 
ness. Table  XXV.  gives  the  values  of  the  constant  C  for 
different  metals  in  English  measures. 

Lord  Kelvin  (then  Sir  William  Thomson)1  has,  however, 
shown  that  the  figures  given  by  Peclet  and  the  earlier  experi- 
menters before  Angstrom,  as  expressing  the  conductivity,  wrere 
in  several  instances  too  small  ;  those  for  the  conductivity  of 
copper,  for  instance,  having  been  200  times  too  small  as  given 
by  Clement,  and  live  times  too  small  as  given  by  Peclet. 

Motion  Essential  to  Transmission,  —  In  considering  the  trans- 
mission of  heat  through  metal  plates  to  or  from  a  gas,  Peclet 
insists  on  the  necessity  for  movement  of  the  particles  in  contact 
with  the  heating  surfaces  for  giving  or  receiving  heat.  In 
his  own  words  :  "  Ainsi  Ton  voit  que,  clans  tous  les  cas,  le 
renouvellement  rapicle  cles  couches  de  liquide  on  de  gaz  qui 
touchent  les  surfaces  de  la  plaque  metallique  a  une  tres-grande 
influence  sur  la  transmission  cle  la  chaleur,  mais  que  cette 
circonstance  est  beaucoup  plus  importante  pour  les  gaz  que  pour 
les  liquicles.  On  doit  done  chercher  la  disposition  des  appareils 
qui  favorise  le  plus  possible  ce  renouvellement,  par  1'effet  seul 
du  mouvement  qui  resulte  de  rechauffement  et  du  refroidisse- 
ment,  et  par  les  mouvemens  que  les  fluides  doivent  prendre  pour 
entrer  et  sortir  des  appareils.  Mais,  pour  les  gaz,  ou  peut  en 
outre  produire  artiticiellement  dans  leurs  masses  des  mouvemens 
qui  occasionnent  un  renouvellement  rapide  des  couches  en 
contact  avec  les  surfaces  metalliques,  soit  par  une  action  directe 
qui  n'exigerait  qu'un  faible  travail,  soit  en  enployant  une  partie 
de  la  force  qui  resulte  de  rcoulement." 

Direction  of  Currents.  —  In  addition  to  this  necessity  for  rapid 
motion,  it  is  also  plainly  necessary,  as  Peclet  indicates,  that  for 
a  complete  exchange  of  temperature  the  currents  of  the  heating 
and  heated  fluids  should  be  caused  to  move  in  opposite 

1  See  article  "  Heal  "  in  Encyclopaedia  Brit.,  ninth  edition. 


THE  MODERN  STEAM  BOILER.  121 

directions.  By  this  method  at  all  points  of  the  travel  of  the 
heating  medium  its  temperature  must  he  higher  than  that  of  the 
substance  being  heated,  so  that  transmission  can  always  take 
place  and  all  the  heating  surface  can  be  made  useful.  When 
both  currents  traverse  the  surface  in  the  same  direction,  they 
can  only  reach  a  mean  temperature,  which  is  soon  attained,  after 
which  the  heating  surface  is  of  no  use. 

In  Chap.  III.  (pages  97-100,  ante)  two  illustrations  of  the 
effects  of  movement  (in  one  of  the  insufficiency  of  the  amount 
of  movement)  on  transmission  of  heat  by  air  and  water  have 
been  given,  viz.,  in  the  case  of  feed-water  and  air  heaters  of 
Mr.  Kemp  and  Mr.  Howden,  and  in  the  case  of  Mr.  Craddock's 
experiments  with  air  and  water  condensers.  The  effect  of  move- 
ment is  illustrated  in  Mr.  Kemp's  apparatus  in  the  fact  that  his 
feed-water  heaters  required  to  have  double  the  heating  surface 
of  his  boilers  in  order  to  heat  the  slow  moving  water  from  130° 
to  270°,  the  hot  gases  being  cooled  from  675°  to  225°,  the  tem- 
perature of  steam  in  the  boiler  being  363-4°  ;  no  steam  was  raised 
in  the  feed  heaters,  but  to  do  this  work  the  boilers  required  only 
half  the  surface  of  the  heaters  and  only  the  movement  of  the 
water  in  the  boilers  can  account  for  a  great  part  of  the  differ- 
ence. There  is  no  doubt,  however,  that  the  higher  temperature 
of  the  hot  gases  in  contact  with  the  boiler  surfaces  would  also 
assist  the  more  rapid  transmission  of  heat. 

Professor  0.  Reynolds  on  Heat  Transmission. — In  1874  Professor 
Osborne  Reynolds  made  a  short  communication  to  the  Man- 
chester Literary  and  Philosophical  Society  "On  the  Extent  and 
Action  of  the  Heating  Surface  for  Steam  Boilers,"  in  which  he 
directed  attention  to  the  influence  of  motion  on  the  transmission 
of  heat ;  and  on  account  of  the  importance  of  the  arguments 
advanced,  this  paper  deserved  to  be  more  widely  noticed  than 
has  been  its  fate.  Professor  Reynolds  pointed  out  that  in  many  of 
the  works  dealing  with  heat  transmission  "  there  is  one  assump- 
tion which  upon  the  face  of  it  seems  to  be  contrary  to  general 
experience,  and  this  is  that  the  quantity  of  heat  imparted  by  a 
given  extent  of  surface  to  the  adjacent  fluid  is  independent  of 
the  motion  of  that  fluid  or  of  the  nature  of  the  surface  ;  whereas 
the  cooling  effect  of  a  wind  compared  with  still  air  is  so  evident 
that  it  must  cast  doubt  upon  the  truth  of  any  hypothesis  which 
does  not  take  it  into  account."  Accordingly,  he  approached  the 


122  THE  PRACTICAL  PHYSICS  OF 

subject  on  the  side  of  the  then  recent  laws  of  the  internal 
diffusion  of  fluids  on  the  molecular  theory  and  thus  stated  his 
position  :  "  The  heat  carried  off  by  air  or  any  fluid  from  a 
surface,  apart  from  the  effect  of  radiation,  is  proportional  to  the 
internal  diffusion  of  the  fluid  at  or  near  the  surface  ;  i.e.,  is  pro- 
portional to  the  rate  at  which  particles  or  molecules  pass  back- 
wards and  forwards  from  the  surface  to  any  given  depth  within 
the  fluid.  Thus,  if  AB  be  the  surface  and  a b  an  ideal  line  in  the 
fluid  parallel  to  AB,  then  the  heat  carried  off  from  the  surface 
in  a  given  time  will  be  proportional  to  the  number  of  molecules 
which  in  that  time  pass  from  a  b  to  AB,  that  is,  for  a  given  differ- 
ence of  temperature  between  the  fluid  and  the  surface.  This 
assumption  is  fundamental  to  what  I  have  to  say,  and  is  based 
on  the  molecular  theory  of  fluids. 

"  Now,  the  rate  of  this  diffusion  has  been  shown  from  various 
considerations  to  depend  on  two  things  : — 

il  i.  The  natural  internal  diffusion  of  the  fluid  when  at  rest. 

"  2.  The  eddies  caused  by  visible  motion  which  mixes  the 
fluid  up  and  continually  brings  fresh  particles  into  contact  with 
the  surface. 

"  The  first  of  these  causes  is  independent  of  the  velocity  of  the 
fluid  ;  if  it  be  a  gas  is  independent  of  its  density,  so  that  it  may 
be  said  to  depend  only  on  the  nature  of  the  fluid.1  The  second 
cause,  the  effect  of  eddies,  arises  entirely  from  the  motion  of  the 
fluid,  and  is  proportional  both  to  the  density  of  the  fluid,  if  gas, 
and  the  velocity  with  which  it  flows  past  the  surface. 

"  The  combined  effect  of  these  two  causes  may  be  expressed 
in  a  formula  as  follows  : — 

H=A/  +  Bpz;/  (i) 

where  /  is  the  difference  of  temperature  between  the  surface 
and  the  fluid,  p  is  the  density  of  the  fluid,  v  its  velocity, 
and  A  and  B  constants  depending  on  the  nature  of  the  fluid, 
H  being  the  heat  transmitted  per  unit  of  the  surface  in  a  unit 
of.  time. 

"  If,  therefore,  a  fluid  were  forced  along  a  fixed  length  of 
pipe  which  was  maintained  at  a  uniform  temperature  greater 
or  less  than  the  initial  temperature  of  the  gas,  we  should  expect 
the  following  results. 

1  "  The  Theory  of  Heat,"  by  J.  Clerk  Maxwell,  chap.  xix. 


THE  MODERN  STEAM  BOILER.  123 

"  i.  Starting  with  a  velocity  zero,  the  gas  would  then  acquire 
the  same  temperature  as  the  tube.  2.  As  the  velocity  increased, 
the  temperature  at  which  the  gas  would  emerge  would  gradually 
diminish,  rapidly  at  hrst,  but  in  a  decreasing  ratio  until  it  would 
become  sensibly  constant  and  independent  of  the  velocity.  The 
velocity  after  which  the  temperature  of  the  emerging  gas  would 
be  sensibly  constant  can  only  be  found  for  each  particular  gas 
by  experiment,  but  it  would  seem  reasonable  to  suppose  that  it 
would  be  the  same  as  that  at  which  the  resistance  offered  by 
friction  to  the  motion  of  the  fluid  would  be  sensibly  proportional 
to  the  square  of  the  velocity.  It  having  been  found,  both 
theoretically  and  by  experiment,  that  this  resistance  is  connected 
with  the  diffusion  of  the  gas  by  a  formula  : 

R  =  AV  +  B>3  (2) 

and  various  considerations  lead  to  the  supposition  that  A  and  B 
in  formula  (i)  are  proportional  to  A1  and  B1  in  (2).  The  value 
of  v  which  this  gives  is  very  small,  and  hence  it  follows  that  for 
considerable  velocities  the  gas  should  emerge  from  the  tube  at  a 
nearly  constant  temperature,  whatever  may  be  its  velocity.  This 
is  in  accordance  with  what  has  been  observed  in  tubular  boilers 
as  well  as  in  more  definite  experiments. 

"In  the  locomotive  the  length  of  the  boiler  is  limited  by  the 
length  of  the  tube  necessary  to  cool  the  air  from  the  fire  down 
to  a  certain  temperature,  say  500°.  Now,  there  does  not  seem  to 
be  any  general  rule  in  practice  for  determining  this  length,  the 
length  varying  from  16  feet  to  as  little  as  6  feet,  but  whatever 
the  proportions  may  be,  each  engine  furnishes  a  means  of  com- 
paring the  efficiency  of  the  tubes  for  high  and  low  velocities  of 
the  air  through  them.  It  has  been  a  matter  of  surprise  how 
completely  the  steam-producing  power  of  a  boiler  appears  to 
rise  with  the  strength  of  blast  or  the  work  required  from  it. 
And  as  the  boilers  are  as  economical  when  working  with  a  high 
blast  as  with  a  low,  the  air  going  up  the  chimney  cannot  have  a 
much  higher  temperature  in  the  one  case  than  in  the  other. 
That  it  should  be  somewhat  higher  is  strictly  in  accordance 
with  the  theory  as  stated  above. 

"  It  must,  however,  be  noticed  that  the  foregoing  conclusion 
is  based  on  the  assumption  that  the  surface  of  the  tube  is  kept 
at  the  same  constant  temperature,  a  condition  which  it  is  easy  to 
see  can  hardly  be  fulfilled  in  practice. 


i24  THE  PRACTICAL  PHYSICS  OF 

"  The  method  by  which  this  is  usually  attempted  is  by  sur- 
rounding the  tube  on  the  outside  with  some  fluid,  the  temperature 
of  which  is  kept  constant  by  some  natural  means,  such  as  boiling 
or  freezing  ;  for  instance,  the  tube  is  surrounded  with  boiling 
water.  Now,  although  it  may  be  possible  to  keep  the  water  at  a 
constant  temperature,  it  does  not  at  all  follow  that  the  tube  will 
be  kept  at  the  same  temperature  ;  but,  on  the  other  hand,  since 
heat  has  to  pass  from  the  one  to  the  other,  there  must  be  a 
difference  of  temperature  between  them,  and  this  difference  will 
be  proportional  to  the  quantity  of  heat  which  has  to  pass.  And 
again,  the  heat  will  have  to  pass  through  the  material  of  the 
tube,  and  the  rate  at  which  it  will  do  this  will  depend  on  the 
difference  of  the  temperature  at  its  two  surfaces.  Hence,  if  the 
air  be  forced  through  a  tube  surrounded  with  boiling  water,  the 
temperature  of  the  inner  surface  of  the  tube  will  not  be  constant, 
but  will  diminish  with  the  quantity  of  heat  carried  off  by  the 
air.  It  may  be  imagined  that  the  difference  will  not  be  great  ; 
a  variety  of  experiments  lead  me  to  suppose  that  it  is  much 
greater  than  is  generally  supposed.  It  is  obvious  that,  if  the 
previous  conclusions  be  correct,  this  difference  would  be 
diminished  by  keeping  the  water  in  motion,  and  the  more  rapid 
the  motion  the  less  would  be  the  difference." 

Experiments  with  Steam. — A  large  proportion  of  the  earlier 
experiments  on  heat  transmission  were  experiments  on  cooling, 
and  those  investigations  which  have  had  evaporation  in  view 
have  usually  been  conducted  with  steam  as  the  heating  agent, 
SD  that  we  still  require  experiments  with  higher  temperature 
differences  and  with  apparatus  more  suited  to  the  conditions 
of  the  inquiry  than  the  small  vessels  which  have  been  used  by 
Hirsch,  Blechynden,  Bryant,  and  others. 

Although  there  has  necessarily  been  movement  of  a  kind 
in  all  the  experiments,  yet  the  effect  of  increased  rates  of 
movement  has  not  been  much  inquired  into.  Of  the  early 
experimenters,  according  to  G.  A.  Hagemann,  only  Colding 
(whose  treatise,-  dated  1864,  is  said  to  have  proved  the  com- 
plete correctness  of  Newton's  law)  attempted  to  determine 
the  influence  of  'speed  on  cooling  ;  and  it  is  the  absence  of 
proper  provision  for  anything  but  very  restricted  movement 
that  greatly  detracts  from  the  value  of  the  experiments 
of  most  of  the  later  investigators.  Colding  reached  only  a 


THE  MODERN  STEAM  BOILER. 


I25 


rough  approximation  to  ji  law  for  the  influence  of  currents. 
Hagemann,1  however,  carried  out  several  series  of  interesting 
experiments,  not  on  cooling,  but  made  with  experimental 
apparatus  which  was  designed  in  view  of  the  evaporation  of 
sugar  and  other  liquors  at  comparatively  low  temperatures. 


/"('.  Temp 


KHJ.  59- 


Experiments. — -A  series  of  experiments  was  under- 
taken to  determine  the  influence  which  speed  of  flow  had  upon 
trtinsiiiission  when  I  lie  temperature-differences  were  constant  and  the 
steam  temperature  was  maintained  at  100°  C.  The  results  are 


Min.  Proc.  Inst.  C.E.,  Vol.  Ixxvii.,  pp.  311-322. 


126  THE  PRACTICAL  PHYSICS  OF 

found  in  the  following  Table,  marked  2A,  and  are  graphically 
represented  by  the  darker  curve  in  Fig.  59,  where  the  velocities  of 
the  water  in  feet  per  second  are  set  off  as  abscissae,  and  the  corres- 
ponding heat-transmission  as  ordinates.  The  points  shown  by 
small  circles  were  determined  by  measurement,  and  the  points 
shown  by  large  circles  were  borrowed  from  lines  found  by  other 
experiments.  A  speed  of  o,  instead  of  giving  no  transmission, 
gave  a  very  perceptible  amount,  which  was  caused  by  the  streams 
generated  in  the  water,  the  same  circulation  which  renders 
possible  a  comparatively  rapid  heating  of  water,  in  spite  of  its 
being  a  bad  conductor.  At  a  temperature  difference  of  51°  C.,  a 
speed  less  than  that  due  to  heating  alone  had  but  little  influence, 
but  with  a  greater  speed  the  influence  was  very  marked,  the 
transmission  increasing  rapidly,  though  not  quite  in  proportion 
to  the  speed. 

After  determining  the  influence  of  speed  at  a  temperature 
difference  of  51°  C.,  another  series  of  experiments  was  under- 
taken to  rind  the  influence  of  temperature  -  differences  at  constant 
speed.  The  results  are  marked  3,  4,  5  and  6  in  the  Table,  and 
are  graphically  represented  by  the  curves  B,  C,  D.  and  E  in 
Fig.  60. 

The  data  for  determining  the  first  portion  of  the  curves  was 
wanting,  but  their  form  was  assumed  from  other  experiments 
and  a  comparison  with  the  boiling  or  evaporation  curve  of  the 
tube,  which  curve  is  shown  at  F. 

From  these  results  it  appeared  that  heat-transmission  per 
degree  was  greatest  at  low-temperature  differences,  but  circum- 
stances prevented  the  determination  of  the  point  at  which 
maximum  transmission  was  reached.  Hagemann,  however, 
supposed  that  the  thermal  conductivity  of  the  heating  surface 
under  the  conditions  of  his  experiments  was  governed  by  the 
film  of  water  which  was  constantly  formed  and  renewed  on  the 
steam  side  of  his  metal  tube.  He  was,  no  doubt,  right  in  this,  as 
Peclet  had  previously  found  that  such  conditions  soon  imposed  a 
limit  to  heat  transmission.  Hagemann  also  undertook  a  series 
of  experiments  to  investigate  the  influence  of  speed  of  water  on  the 
heat  transmission]  which,  as  he  justly  observes,  is  an  important 
factor  to  be  considered.  The  results  of  this  series  are  given  in 
the  following  Table,  marked  8,  9,  10  and  n,  with  the  curves 
G,  H,  I,  and  J,  shown  in  Fig.  60. 


THE  MODERN  STEAM  BOILER. 


127 


S  9  t  St 


128 


THE  PRACTICAL  PHYSICS  OF 


TABLE  XXVI. 

HAGEMANN   ON  TRANSMISSION   OP  HEAT. 


1  No.  of  Experiment. 

Steam. 

Water 

Temperature-difference.! 

Quantity  of  Water 
in  Ibs. 

Time. 

Heat- 
units 
trans- 
mitted 
per 
Minute. 

Apparent  Temperature- 
difference  Centi- 
grade. 

Heat-units  transmitted 
1°  Difference  1  Minute 
1  Square  Foot. 

Velocity  of  Water  in 
Feet  per  second. 

Reference  No.  to  Table! 
and  letter  to  Plate.  | 

1  Pressure  in  Ibs. 
per  sq.  in. 

Temperature 
Centigrade. 

i 

At  Outflow. 

0 

o 

o 

o 

Min.sec 

o 

4 
5 

0 
0 

100 
100 

26-1 

25-8 

70-6 
70-7 

44-5 
44-9 

25-4 
25-4 

5    0 
5    0 

225-7 

227-5 

51-7 
51-8 

J3-04 

0-30 

} 

6 

7 

0 
0 

100 
100 

32-2 
32-2 

63-7 
63-4 

31-5 
31-2 

39-0 
38-6 

5    0 
5    0 

250-6 
240-7 

52-2 
52-2 

J3-29 

0-46 

8 

0 

100 

37-0 

58-8 

21-8 

77-6 

5    0 

338-2 

52-1 

\A.A1 

0,  Q(~\ 

9 

0 

100 

36-8 

58-7 

21-9 

72- 

5    0 

316-6 

52-1 

>4  4J 

oJ 

10 

0 

100 

41-3 

56-C 

14-7 

88- 

2    0 

651-2 

51-4 

}o  .IJK 
8  75 

2  -no 

2.  A. 

11 

0 

100 

41-2 

56-0 

14-8 

86' 

2    0 

643-8 

51-4 

OL 

lla 

0 

100 

41-3 

52-9 

11-6 

101- 

1  30 

757-9 

52-9 

9-99 

4-06 

116 

0 

100 

42-8 

51-4 

8-6 

95* 

1    0 

826-0 

52-7 

10-94 

5-57 

He 

0 

100 

41-2 

50-5 

9-3 

113- 

i  10 

904-7 

54-2 

11-65 

5-67 

lid 

0 

100 

50-7 

58-0 

7-3 

99- 

1    .0 

729-7 

45-7 

11-14 

5-93 

12 

0 

]00 

88-9 

93-6 

4-7 

85- 

5    0 

80-2 

8-8 

6-35 

1-02 

13 

0 

100 

86-4 

92-0 

5-6 

85- 

5    0 

95-7 

10-8 

6-17 

1-02 

14 

0 

100 

73-4 

83-9 

10-5 

86;  4 

5    0 

183-4 

21-3 

5-98 

1-03 

15 

0 

100 

56-8 

72-7 

15-9 

86-4 

5    4 

275-0 

35-3 

5-43 

1-03 

16 

0 

100£ 

47-8 

66-9 

19-1 

87-5 

5    0 

334-0 

42-7 

5-45 

1-04 

^3.  B. 

17 

0 

ioo| 

40-0 

61-4 

21-4 

69-9 

4    0 

368-1 

49-3 

5-19 

1-02 

18 

0 

100J 

35-5 

57-3 

21-8 

86-4 

5    0 

377-1 

53-6 

4-90 

1-03 

19 

0 

100J 

28-9 

51-7 

22-8 

85-3 

5    0 

389-5 

59-7 

4-55 

1-02 

20 

0 

ioo| 

15-9 

41-7 

25-8 

87-5 

5    0 

452  -.1 

72-2 

4-36 

1-04 

1 

21 

0 

100 

88-5 

92-1 

3'6 

75-0 

2    0 

137-9 

9-7 

9-66 

2-23 

22 

0 

100 

88-0 

91-7 

3-7 

73-6 

2    0 

136-0 

10-2 

9-29 

2-19 

23 

0 

100 

86-0 

9Q-4 

4-4 

70-3 

2    0 

154-5 

11-8 

9-14 

2-09 

24 

0 

100 

70-5 

79-8 

9-3 

70-3 

2    0 

326-6 

24-9 

9-14 

2-07 

25 

0 

100 

70-3 

79-3 

9-0 

69-9 

2    0 

314-3 

25-2 

8-69 

2-08 

^4.0. 

26 

0 

100 

55-1 

67-8 

12-7 

69-9 

2-    0 

443;  5 

38-6 

8-17 

2-08 

27 

0 

100 

40-5 

56-0 

15-5 

70-3 

2    0 

544-9 

51-8 

7-29 

2-09 

28 

0 

100 

30-7 

46-2 

15-7 

70-5 

2    0 

553  ;  8 

61-7 

6-22 

2-10 

29 

0 

100 

9-8 

28-6 

18-8 

69-9 

2    0 

656-7 

80-8 

5-65 

2-08 

30 
SI 

0 
0 

100 
100 

90-8 
90-8 

93-0 

92-8 

2-2 
2-0 

56-6 
56-2 

1     0 
1     0 

124-6 
112-4 

8-n 
8-2; 

10-14 

3-35 

00 

0 

100 

85-4 

89-2 

3-8 

65-0 

10 

211-8 

12-7 

11-59 

3-31 

33 

0 

100 

60-5 

70-0 

95 

57-5 

0 

546-0 

34-8 

10-90 

3-41 

I5.D. 

34 

0 

100 

43-5 

56-5 

13-0 

57-1 

0 

741-2 

50-0 

10-34 

3-40 

35 

0 

100 

9-5 

25-3 

15-8 

56-6 

0 

895-1 

82-6 

7-53 

3-38 

36 

0 

100 

89-7 

91-4 

1-7 

90-4 

0 

159-2 

9-5 

11-68 

5-38 

37 

0 

100 

72-0 

78-2 

6-2 

91-4 

0 

567-2 

24-9 

15-90 

5-44 

'GE 

38 

0 

100 

52-8 

61-6 

8-8 

107-4 

1.0 

809-0 

37-8 

14-91 

5-46 

O.  i-j. 

39 

0 

100 

9-6 

22-2 

12-6 

90-4 

0 

1,138-9 

84-1 

9-53 

5-38 

40 

0 

100 

9-6 

21-5 

11-9 

77-2 

0  50 

1,102-3 

78-9 

9-66 

5-50 

THE  MODERN  STEAM  BOILER. 


129 


TABLE  XXVII. 


f 

Steam. 

Water 

1 

s 

1 

sJL 

3  ^ 

!« 

s 

(a 

£• 

Heat- 

8 

§  s  g 

•£»  g 

ss! 

I 

£  . 

""  C 

S*""1 

g 

1 

1 

1 

•^*.S 

Time. 

units 
trans- 
mitted 

s| 

111 

It 

62 

% 

I- 

It 

P, 

H 

a 

| 

1 

1 

Of 

per 
Minute. 

1=3 
5 

jt- 

£>  A 

Jig 

* 

H 

•aj 

K-1 

tf 

o 

o 

0 

o 

Min  sec. 

0 

56 

0 

104-4 

5-5 

30-8 

25-3 

99-2 

3     2* 

826 

86-2 

6-67 

1-94 

57 

10 

115-0 

5-7 

36-5 

30-8 

99-2 

3    9 

970 

93-9 

7-19 

1*87 

Q     fi 

58 

20 

124-0 

5-6 

40-2 

34-6 

99-2 

3  11 

1,071 

101-2 

7-37 

1-83 

o.  VT.  • 

59 

41 

138-2 

5-6 

47-2 

41-6 

99-2 

3    9 

1,309 

111-3 

8-19 

1-87 

(30 

0 

100-4 

5-8 

29-2 

23-4 

99-2 

2  46 

844 

82-9 

7-07 

2-14 

61 

0  100-5 

5-8 

29-8 

22-0 

99-2 

2  46 

864 

82-7 

7-21 

2-14 

62 

8112-8 

6-0 

35-4 

29  4 

99-2 

2  47 

,060 

92-1 

7  98 

2-14 

Q  TT 

63 

14 

119-8 

6-0 

38-0 

32-0 

99-2 

2  45 

,153 

97-8 

8-20 

2-14 

•«-'•  Jti. 

64 

16122-5 

6-0 

39-0 

33-0 

99-2 

2  45 

,190 

100-0 

8-30 

2-14 

65 

32133-2 

6-0 

44-2 

38-2 

99-2 

2  45 

,378 

108-1 

8-91 

2-14 

66 

0100-5 

6-0 

26-2 

20-2 

99-2 

2    0 

,003 

84-5 

8-30 

2-95 

67 

0 

107-0 

6-0 

28-6 

22-6 

99-2 

2    0 

,120 

89-7 

8-79 

2-95 

68 

11 

116-0 

6-0 

31-0 

25-0 

99-2 

2    0 

,239 

97-5 

8-83 

2-95 

mT 

69 

14 

119-4 

6-0 

32-4 

26-4 

99-2 

2    0 

,309 

100-2 

9-05 

2-95 

•  x. 

70 

29 

131-5 

6-0 

35-8 

29-8 

99-2 

2    0 

,477 

110-6 

9-27 

2-95 

71 

29 

131-0 

6-0 

35-6 

29-8 

99-2 

2    0 

,477 

110-3 

9-27 

2-95 

72 
73 

74 

0 
0 
0 

100-0 
100-0 
105-0 

6-4 
6-5 

6-8 

20-8 
20-8 
22-2 

15-4 

77-1 

77-1 

0  59 
0  59 

,111 

,188 

86-4 
90-5 

8-91 
9-14 

4-59 

4-59 

i 

75 

9 

113-2 

6-8 

23-6 

15-8 

77-1 

0  59 

,296 

98-0 

9-21 

4-59L,   T 

76 
77 

22 
22 

126-0 
125-0 

6-5 
6-4 

26-6 
26-2 

J20-0 

77-1 

0  59 

1,543 

109-1 

9-89 

4-59 

fa.  «j. 

\ 

78 
79 

28 
28 

130-5 
129-4 

6-3 
6-3 

26-6 
26-6 

J20-3 

77-1 

1     0 

1  ,-565 

1 

113-6 

9'48 

4-59. 

\ 

He  remarks  on  these  curves,  "It  is  a  natural  result  of  the 
method  of  experiment  adopted,  that  the  parts  of  the  curves  of 
transmission  actually  determined  are  not  greater  and  begin 
rather  high  up,  but  the  principal  result  obtained  previously,  namely, 
that  Hie  transmission  of  heal  increases  ivitli  increasing  speed,  is 
further  confirmed"  These  are  amongst  the  most  important  of 
his  results,  and  their  value  is  certainly  not  lessened  by  the  very 
sensible  and  modest  remarks  with  which  he  closes  his  excellent 
paper.  "  The  foregoing,"  he  writes,  "are  the  results  of  a  series 
of  careful  experiments  on  some  of  the  conditions  affecting  the 
heat-transmitting  power  of  one  form  of  heating  surface,  from 
which  the  experimenter  hopes  practical  men  may  be  able  to 
obtain,  at  any  rate,  some  little  information.  Xo  attempt  is  made 
to  deduce  a  general  law  from  these  experiments,  owing  to  their 


130 


THE  PRACTICAL  PHYSICS   OF 


comparatively  limited  range,  and  to  the  neglect  of  several 
important  factors,  such  as  the  form  and  position  of  the  heating 
surface,  the  thermal  conductivity  of  the  metal  forming  it,  and 
the  specific  heat  of  the  liquid  receiving  the  heat." 

It  would  be  well  if  all  experimenters  were  able  to  take  a 
similarly  comprehensive  view  of  the  problems  which  they  essay 
to  solve.  "  Laws "  and  "  rules "  have  often  been  hastily 
formulated  on  a  much  more  slender  basis  of  facts  than  those  of 
Hagemann's  careful  experiments  ;  no  doubt  under  the  mistaken 
notion  that  a  "law"  gives  permanence  to  the  experiments, 
instead  of  its  being  in  epitome  the  ultimate  truth  of  the  subject 
investigated. 

NichoVs  Experiments. — Some  good  experiments  on  surface 
condensation  of  steam  were  carried  out  in  1875  by  Mr.  B.  G. 
Nichol,1  the  condensing  water  having  been  passed  through  a 
brass  tube  f  in.  diameter  outside,  which  was  enclosed  in  an  iron 
pipe  3!  in.  diameter  outside  and  J-  in.  thick,  leaving  a  space 
of  about  i  j-  in.  round  the  brass  tube  for  the  steam. 

The  condensing  tube  acted  more  efficiently  in  a  horizontal 
than  in  a  vertical  position  ;  a  result  said  to  be  the  reverse  of 
what  had  been  found  by  M.  Clement  when  condensing  in  air. 

The  following  are  the  velocities  of  the  water  through  the  tube 
in  feet  per  minute,  and  the  corresponding  number  of  (British) 
heat  units  absorbed  by  the  water  per  square  foot  of  heating 
surface  per  hour,  per  i°  F.  difference  of  temperature. 


Vertical  tube. 

Horizontal  tube. 

Velocity 

81 

278 

390 

78 

307 

415 

Heat  units    ... 

346 

449 

466 

479 

621 

696 

The  difference  of  temperatures  of  the  steam  and  the  con- 
densing water  were  255°— 58°=  197°. 

It  appears  from  these  experiments  that  the  efficiency  of 
the  heat-transmitting  surface  was  much  increased  by  an  increase 
in  the  velocity  of  the  movement  of  the  water.  The  velocity  of 
the  steam  over  the  cooling  surface  is  not  stated.  The  brass 


1  See  Engineering,  December  loth,  1875. 


THE  MODERN  STEAM  BOILER.  131 

tube  had,  however,  a  cooling  surface  of  1-0656  square  feet, 
and  the  area  of  the  steam  space  was  77640  square  inches. 
The  brass  tube  was  5ft.  5ins.  long,  and  the  weight  of  steam 
condensed  per  square  foot  of  tube  per  hour  was 

52-32  |  78-18  |  84-3411  67-8  |  104-6 |i2i-3lbs. 
Professor  SeSs  Results. — Some  systematic  investigations  of  the 
effect  of  increase  of  velocity  upon  heat  transmission  have  been 
made  by  Professor  Ser *  of  the  College  of  Arts  and  Manufactures 
in  Paris,  whose  experiments  have  been  utilised  in  connection  with 
the  evaporation  of  liquids2  long  before  their  bearing  upon  boiler 
practice  was  appreciated.  In  determining  the  effect  of  the  rapid 
motion  of  water  over  the  heating  surface  he  used  the  following 
apparatus.3  (See  Fig.  61.)  It  consisted  of  a  thin  horizontal  copper 


FIG.  6l. 

tube,  A  B,  of  a  foot  in  length  and  four  inches  internal  diameter, 
terminating  at  either  end  in  a  short  length  of  vertical  tube  with 
a  branch.  The  water  entered  at  C,  and  flowing  through  A  B, 
passed  out  at  D,  thermometers  a  and  b  being  respectively  placed 
in  the  vertical  chamber  at  each  end  of  A  B  to  show  the  tempera- 
ture of  the  water  on  entering  and  on  leaving  the  tube.  The 
tube  A  B  was  surrounded  by  a  jacket  or  casing  M  N  P  Q,  with 
branches  similar  to  the  end  chambers  of  A  B.  This  casing  was 
also  of  copper,  and  the  whole  apparatus  was  covered  with 
wadding  to  prevent  radiation.  Steam  \vas  passed  into  the  casing 

1  Traits  dc  Physique  Industrielle.    Vols.  i.  ii.     Paris,  1887-1891. 

2  "  Evaporation  by  the  Multiple  System,"  by  James  Foster.   Second  Edition, 
p.  562.     Sunderland,  1895. 

3  "  Halliday's  Paper    Inst.    Marine    Engineers,"    also    "  The  Mechanical 
Engineer,"  Nov.  26,  1898,  p.  786, 

F  2 


132 


THE  PRACTICAL  PHYSICS  OF 


by  the  branch  at  E,  and  out  at  F,  its  temperature  at  entering 
and  issuing  being  taken  by  thermometers  at  m  and  n.  The 
temperature  of  the  heating  medium  being  constant,  the  effect  of 
giving  different  velocities  to  the  water  upon  the  rate  of  heat 
transmission  is  shown  by  the  following  figures  : — 

TABLE  XXVIII. 


Speed  of  water 
through  tube  ; 
metres  per  second. 

Coefficient  of 
heat 
transmission. 

Speed  of  water 
through  tube  ; 
metres  per  second. 

Coefficient  of 
heat 
transmission. 

•I 

1,400 

7 

3,180 

•2 

2,230 

•8 

3,330 

•3 

2,550 

'9 

3,48o 

'4 

2,710 

ro 

3,640 

'5 

2,860 

ri 

3,800 

•6 

3,020 

These  results  have  been  graphically  represented  by  the 
following  curve,  and  they  deserve  much  attention,  seeing  that 
they  were  obtained  in  spite  of  the  very  short  travel  of  the  wrater 
through  the  tube  A  B,  and  also  uf  the  fact  that  the  currents  of 
both  steam  and  water  were  passed  in  the  same  direction — both 

of   these   being   conditions 

4000rm  m  1 1  i  1 1 1  i  1 1 1  i  i  i  1 1  i  i  n     which  militate  against  the 

most  favourable  result  being 
obtained. 

It  is  nevertheless  evident 
that  a  considerable  gain  in 
efficiency  of  transmission 
is  obtained  by  an  increased 
speed  of  movement  of  the 
water  over  the  heating 
surface,  the  curve  rising 
steadily  all  the  time,  al- 
though more  rapidly  at  the 
commencement,  between 
the  velocities  of  'i  and  '3 
metre  per  second.1 


u.    2SOO 
o 


5    2000 

u 

5 


1000 


3  4  -56 


-9  1  1.7 


SPEED    JN    METRES    PER    SECOND. 


FIG.  62. 


Halliday's  Paper,  Inst.  Marine  Engineers. 


THE   MODERN   STEAM  BOILER.  133 

i 

Mr.  G.  Halliday '  has  observed  that  from  the  latter  part  of  the 
curve — i^fj  from  -3  to  ri  metre  per  second — the  results  yield 
the  following  calculation  for  coefficient  of  transmission  : — 

Q  =  2,080+  156  x  velocity  of  the  water, 

which  shows  that  the  increase  in   efficiency  is  proportional  to 
the  velocity. 

M.  Ser  has  himself  remarked  that  "  the  transmission  of  heat 
for  the  same  difference  of  temperature  is  more  than  tripled 
when  the  liquid  is  boiling,  which  is  due  to  the  greater  speed  in 
the  circulation  of  the  heated  liquid." 

Now,  the  application  of  this  fact  to  the  natural  motion  of 
water  when  boiling  is  not  the  best,  or  by  any  means  a  final  one  ; 
although  it  may  serve  to  show  that  certain  water-tube  boilers, 
or  feed  heaters,  on  account  of  the  restricted  size  of  their  water 
channels  or  passages,  must  have  a  more  rapid  circulation,  and 
therefore  should  give  better  results,  than  others.  The  question 
before  us  demanding  a  solution  is  not  (or  is  only  partially)  what 
is  the  speed  of  circulation  actually  attained  in  any  individual 
feed-heater,  or  boiler,  or  boiler-model  ;  but  it  is,  what  is  the  best 
speed  for  the  water  so  that  the  greatest  amount  of  heat  trans- 
mission can  be  attained  ?  As  far  as  M.  Ser's  results  show,  the 
speed  may  be  increased  much  beyond  his  figures  with  corres- 
pondingly good  effect. 

Investigation,  by  the  same  experimenter,  of  the  effect  of 
motion  on  the  transmission  of  heat  to  air  or  gases,  yielded 
results  showing  advance  in  a  similar  direction.  In  this  case,  the 
experiments  were  carried  out  in  tubes  of  -25  metre  in  diameter, 
having  fifty  radial  projections,  or  ribs,  similar  to  those  of  a  Serve 
tube.  The  height  of  these  projections  was  -05  metre,  and  they 
had  a  thickness  of  *oo8  metre  at  their  base,  and  '002  metre  at  the 
top.  The  heating  surface  of  each  tube  was  5-40  square  metres, 
one  being  placed  in  a  cylinder,  or  larger  tube,  leaving  for  the 
passage  of  the  air  to  be  heated  an  annular  space  of  '0488  of 
a  square  metre  in  sectional  area  ;  the  other  tube  was  placed  in 
a  rectangular  box,  which  gave  a  space  round  the  tube  for 
the  air  passage  of  -098  square  metre  in  sectional  area — the 
area  of  the  one  passage  was  thus  practically  double  that  of 
the  other. 

1  Trans.  Inst.  Marine  Engineers,  Vol.  x,  yjth  Paper,  p.  13. 


134  THE  PRACTICAL  PHYSICS  OF 

The  following  are  the  results  obtained  : — 
TABLE  XXIX. 


Sectional  area  of  passage  tor  air,  -098  square  metre. 

Sectional  area  of  passage  for  air,  -0488  square  metre. 

Speed  through  the  passage 
in  metres  per  second. 

Coefficient  in  calories  per 
square  metre  per  hour. 

Speed  through  the  passage 
in  metres  per  second. 

Coefficient  in  calories  per 
square  metre  per  hour. 

•42 

4'80 

I-I37 

6-8 

•48 

4'12 

1-318 

7-66 

'57 

4-82 

i-35o 

774 

•58 

4-82 

1-369 

7-88 

•65 

4-88 

1-648 

8-56 

•68 

4-98 

1-684 

8-66 

75 

5'o6 

1-884 

9-42 

•80 

5-94 

1-930 

9-00 

1-047 

7-52 

2-360 

10-44 

These  results  show  that  there  is  a  decided  advantage  in  increas- 
ing the  velocity  of  travel  of  the  gaseous  body,  and  that  the 
transference  of  heat  increases  in  a  greater  ratio  at  the  higher 
velocities. 

C.  R.  Lang's  Experiments. — Amongst  the  most  interesting,  and 
certainly  the  most  successful,  of  experiments  involving  the  trans- 
mission of  heat  from  steam  to  water  across  metal,  are  those  of 
Mr.  C.  R.  Lang !  on  evaporation.  Mr.  Lang's  experiments  were 
carried  out  in  a  Weir's  evaporator  of  the  ordinary  type,  used  to 
make  ten  tons  of  fresh  water  per  day  of  24  hours.  It  is  shown 
in  Figs.  63, 64,  and  65.  The  shell  consisted  of  a  steel  cylindrical 
vessel,  3ft.  diameter  by  4ft.  3in.  long.  The  heating  surface  was 
composed  of  12  solid-drawn  copper  tubes  i^in.  external  diameter 
(i  Jin.  internal  diameter),  giving  a  total  heating  surface  of  38  square 
feet.  The  tubes  were  bent  to  the  shape  known  as  the  "  horse- 
shoe "  or  U  shape,  and  were  arranged  horizontally  in  the  bottom 
part  of  the  cylinder,  in  diagonal  rows  for  convenience  of  scaling. 
The  shape  also  gave  a  certain  freedom  of  expansion  without 
causing  any  strain  upon  the  joints  at  the  ends.  The  tubes  were 


1  "On'Evaporation,"  by'C.  R.  Lang.     Trans.  Inst.  Eng.  and  Shipbuilders  in 
Scotland,  Vol.  xxxii.,  p.  287  (1889). 


THE  MODERN  STEAM  BOILER. 


135 


also  arranged  with  Messrs.  Weir's  device  of  contracted  ends 
and  a  return  tube,  this  being  an  arrangement  which  in  practice 
was  found  to  cause  the  steam  to  pass  continually  and  equally 
through  all  the  tubes,  preventing  any  lodgment  of  air  or  water 
in  them  to  impair  the  efficiency  of  the  surface,  whilst  the  return 
tube  carried  off  all  the  condensed  water  ;  and  any  steam  which 
passed  uncondensed  through  the  contracted  ends  of  the  other 


FIG.  63. 

tubes  was  condensed  in  it.  The  experiments  were  carried  out 
in  seven  distinct  sets  of  three  to  five  different  experiments,  with 
a  different  initial  steam  pressure  in  the  tubes  for  each  set,  the 
steam  pressure  in  the  shell  being  raised  through  each  set.  The 
first  three  sets  were  carried  out  with  the  full  amount  of  heating 
surface,  but  it  was  found  that  at  higher  pressure  the  supply  of 
steam  from  the  boiler  was  inadequate,  and  in  the  last  four  sets 
the  surface  was  reduced  to  21-95  square  feet  by  plugging  up 


136 


THE:  PRACTICAL  PHYSICS  OF 


both  ends  of  five  of  the  tubes.  Salt  water,  having  a  density  of 
19  oz.  of  salt  to  the  gallon,  was  used  in  the  evaporator.  The 
steam  evaporated  from  the  salt  water  could  be  either  led  to  a 
condenser  or  blown  direct  to  the  atmosphere. 

Pressure  gauges  showed  the  pressures  in  the  direct  tubes,  in 


StCTIONAL    ELEVATION    OF    EVAPORATOR 
FIG.    64. 


SECTIONAL     fl^AN     OF     EVAPORATOR      TUBCS 
FIG.   65. 

the  return  tube  and  in  the  steam  space  of  the  shell.  The  area 
of  the  12  tubes  at  ij  in.  internal  diameter  is  147252  square 
inches,  and  that  of  seven  tubes  of  same  diameter  is  8-5897  square 
inches.  On  account  of  the  bend  in  the  tubes  the  velocity  of  the 
passage  of  the  steam  through  them,  which  would  be  simply  due 
to  the  difference  of  pressure,  would  be  slightly  diminished.  It  is 


THE  MODERN  STEAM  BOILER.  137 

remarkable  that  the  best  results  were  obtained  with  the  smaller 
amount  of  heating  surface  and  the  higher  pressures  of  steam, 
causing  a  greater  velocity  of  steam  through  the  tubes  in  these 
experiments.  In  the  cases  of  the  first  (Ai)  and  the  last  (G4) 
experiments  in  the  following  table,  the  linear  velocity  of  the 
steam  was  14^9  feet  per  second,  and  47*5  feet  per  second. 
The  results  of  the  experiments  are  given  in  Table  XXX. 
Regarding  this  Table,  Mr.  Lang  remarked,  "  Column  10  gives 
the  actual  weight  of  boiler  steam  condensed  in  the  tubes  per 
hour,  taken  by  a  weighing  machine  (Pooley's).  The  total  heat 
given  up  by  each  pound  of  steam  condensed  in  the  tubes  was 
plainly  the  difference  between  the  total  heat  of  the  steam  entering 
the  tubes  and  the  total  heat  of  the  water  leaving  the  drain  valve. 
Thus,  let 

Q=a  quantity  of  steam  condensed  in  tubes  (in  Ibs.  per  hour). 

S= total  heating  surface  (in  square  feet). 

H  =  No.  of  heat  units  given  up  per  Ib.  steam  condensed  in  tubes. 

T= temperature  of  steam  in  tubes  (in  degrees  F.). 
/=  „  „  shell  „ 

L= latent  heat  of  steam  in  shell. 
Then  the  heat  units  transmitted  per  square  foot  of  heating  sur- 

QTT 

face  per  hour  =  ^-  (Column  14). 

o 

Lbs.  water  evaporated  per  square  foot  per  hour 

=|~  (Column  15). 

Heat  units  transmitted  per  square  foot  per  hour  for  i°  F.  differ- 
ence of  temperature  =  — ^ (Column  16). 

b(T  — /) 

Lbs.  water  evaporated  per  square  foot  per  hour  for  i°  F.  differ- 
ence of  temperature  =  Qr7. —  (Column  17)." 
SL(  1  — /) 

The  leading  relations  between  these  figures  are  shown  graphi- 
cally in  various  sets  of  curves,  of  which  the  specimen  on  page  143 
is  reproduced  as  bearing  most  directly  on  our  immediate  sub- 
ject. In  Fig.  66  the  ordinates  show  the  number  of  heat  units 
transmitted  per  square  foot  of  heating  surface  per  hour  for 
i  F.  difference  of  temperature,  the  abscissae  showing  the 
number  of  degrees  F.  difference  of  temperature  between  the 
tubes  and  the  shell, 


THE  PRACTICAL  PHYSICS  OF 


" 


Vf  i>«      o^  b 

s.s  II 


•8 


N  ro  r<)  (S 


w  o"  ro   "S  p"^     ID       2  |   ro^  ^  N   .'Ro  cT'R  ??' 


ro    M  ci  ID    «  p)  \o 


I      I       . 

II 

a    'B    " 


. 

8s  M' 

^ 


iwi 


P<  ^C   M      -TOO 


&  8,8 


\o  \o  o^ 

s^s 

00  00  00 


•*•*  ~ 

pi 


MD     \O   rj-b^ 

8  &S£ 


K  3     S" 


MO    ^ 

ro  i>  co 


"  P^O  I?  |  r^^^ 
|«  Jf  ^   JS^^ 


M    ON       000 


ft 


Temper 
Fahre 


TfCOOO 
Tf  rf  CO 


t>  s  v 

ID  ft 
M  « 


pr 
ar 


S3* 


I     I     1 


li 

CO 


tw>  ro 
^'r? 


O^oo  u">  ro 


w  roNOOO 


O  roMOO 
ID  Tj-  P) 


00   Ulio  O 
t>  t^^c  "" 


THE  MODERN  STEAM  BOILER. 


139 


Several  of  the  curves  show  graphically  the  facts  set  forth  in 
column  16,  by  attaining  a  maximum  height  and  then  descending. 
Mr.  Lang  observed  that  "  this  seems  to  indicate  that  for  each 
pressure  in  the  tubes  there  is  a  corresponding  pressure  in  the 
shell  at  which  the  efficiency  of  the  evaporator  is  a  maximum  ; 
and,  further,  that  if  we  draw  a  curve  which  will  be  a  medium 
between  all  the  curves,  the  new  curve  will  show  the  increase  of 
efficiency  of  the  evaporator  as  the  difference  of  temperature 
increases.  This  curve  is  shown  dotted  in  Fig.  66."  It  seems, 


Heat  units. 


1300-E 


eoo 


HOO-r 


700 


10 


"I 

so 


'II' 


JO  40  90  eo 

Degrees  F.  Difference  of  Temperature. 
FIG.  66. 


n  nmiiii  ( 

70  60 


90 


100 


however,  to  be  more  likely  that  the  transmission  of  heat  was 
hindered  beyond  a  certain  point  by  the  want  of  rapid  circula- 
tion of  the  water  in  the  shell.  The  shell  contained  about  885  Ibs. 
of  water,  and  in  the  various  short  periods  through  which  the  ex- 
periments extended,  the  actual  quantity  fed  in  would  necessarily 
be  small,  because  at  the  highest  rate  of  evaporation  attained, 
viz.,  140-23  Ibs.  per  square  foot  per  hour,  the  total  quantity  re- 
quired per  hour  would  be  3,078  Ibs.,  or  little  more  than  three 
times  (about  3^  times)  the  original  quantity  contained  in  the 


HO  THE  PRACTICAL  PHYSICS  OF 

shell.  The  circulation  of  the  water  would,  therefore,  be  practi- 
cally dependent  only  on  the  movement  produced  by  the  heat 
and  steam  in  the  water  in  the  shell  (i.e.,  it  would  not  be  assisted 
by  the  introduction  of  colder  feed  water),  and  the  arrangement 
of  heating  tubes  is  such  as  would  not  assist  the  descent  of  the 
water  to  the  lower  rows.  It  is  in  favour  of  the  chance  of  free- 
dom of  circulation,  however,  that  one  side — the  incoming  side — 
of  the  U  tubes  is  shown  by  the  Table  to  have  been  some  degrees 
hotter  than  the  other  side,  and  consequently  the  whole  body  of 
the  water  would  tend  to  ascend  at  that  side,  and  descend  at  the 
other  side  of  the  shell.  Even  at  the  best,  however,  it  would  not 
be  very  rapid  movement,  and  it  is  more  than  likely  that  the 
efficiency  of  the  evaporator  was  limited  by  the  circulation. 
It  was  distinctly  in  favour  of  these  experiments  that  the  lower 
and  higher  degrees  of  temperature  were  thus  properly  applied  in 
relation  to  the  direction  of  movement  of  the  water,  so  that  the 
descending  water  was  exposed  to  the  lowest  degree,  and  then 
the  highest  temperature  and  the  ascending  water  met.  This 
was,  no  doubt,  what  the  apparatus  adjusted  itself  to  in  the  natural 
course  of  its  action,  but  it  was  an  element  in  its  successful 
working.  Had  the  movement  of  the  water  been  made  more 
rapid,  probably  a  better  result  would  have  followed.  Never- 
theless, the  results  obtained  with  it  have  surpassed  any 
others  as  yet  obtained  in  transmitting  heat  from  steam  to 
water. 

Mr.  Lang  justly  remarks  on  this  point  :  "On  comparing  our 
results  with  those  previously  obtained,  we  find  that  the  best 
results  hitherto  published  have  been  those  of  Peclet.  Using  a 
copper  tube,  137*8  feet  long,  1-36  in.  outside  diameter,  made 
into  a  coil,  with  steam  at  45  Ibs.  pressure  admitted  freely  into  one 
end  of  the  tube,  his  highest  result  was  948  units  of  heat  trans- 
mitted per  square  foot  of  heating  surface  per  hour  for  i°  F. 
difference  of  temperature.  In  another  experiment,  using  two 
coils  of  copper  pipe,  52-5  ft.  long,  1*36  in.  diameter,  he  obtained 
a  still  higher  result,  viz.,  1,120  units.  These  results  have  usually 
been  looked  upon  as  inaccurate,  as  being,  in  fact,  too  high,  but 
on  referring  to  column  16,  it  will  be  seen  that  not  only  have  we 
reached  the  same  figures,  but  that  many  of  our  results  are  a  good 
way  ahead  of  Peclet's,  his  highest  result  being  1,120,  while  our 
highest  is  1,334." 


THE  MODERN  STEAM  BOILER.  141 

The  results  of  the  experiments  F  No.  4  and  G  No.  4,  although 
not  the  highest  in  point  of  number  of  heat  units  transmitted  per 
degree  difference  of  temperature,  are  most  remarkable  from  the 
point  of  view  of  quantity  of  water  evaporated  per  square  foot  of 
surface  per  hour,  one  showing  135*33  Ibs.  of  water  evaporated, 
where  the  temperature  difference  was  997°  F.,  and  the  other 
140-23  Ibs.  of  water,  with  a  temperature  difference  of  1067°  F. 
The  results  of  04,  £5,  F3  and  4  ancl'G2,  3  and  4,  form  a  remark- 
able series  of  evaporative  results  in  connection  with  the  subject 
of  the  utilisation  of  heating  surface  in  steam  boilers,  and  they 
ought  to  prevent  any  rash  conclusions  as  to  the  rate  of  heat 
transmission  in  steam  raising,  based  merely  on  trials  of  boilers 
or  of  apparatus,  which,  in  the  light  of  these  results,  should  be 
acknowledged  to  be  imperfect. 

Experiments  with  Fire  Gases. — We  have  now  to  consider  experi- 
ments made  with  fire  gases  or  flame  as  the  heating  medium,  and 
it  is  at  once  jnanifest  that  we  are  here  confronted  with  enor- 
mously greater  temperature  differences  than  those  which  have 
obtained  in  the  experiments  already  considered.  At  the  first 
glance  we  should  therefore  expect  to  see  much  larger  results  in 
heat-units  transmitted  and  water  evaporated  per  square  foot  of 
heating  surface.  Instead  of  that,  however,  we  are  face  to  face 
with  the  fact  that,  except  in  one  or  two  experiments,  the  best 
results  hitherto  obtained  have  been  far  below  those  which,  as  we 
have  just  seen,  are  attained  in  practice  in  evaporation  by  means  of 
steam.  That  is  unfortunately  the  result  in  boilers  considered  as 
a  whole,  but  these  low  results  are  undoubtedly  due  to  the  greater 
extent  of  heating  surface  which  such  boilers  possess,  in  com- 
parison with  other  apparatus,  a  great  part  of  which  surface  is  so 
used  as  to  be  very  inefficient,  whilst  its  presence  reduces  the 
apparent  efficiency  of  the  more  useful  portions.  Evidence  of 
this  is  to  be  found  in  the  records  of  some  early  experiments  with 
boilers  which  were,  however,  undertaken  to  ascertain  only  the 
manner  in  which  the  heat  of  the  furnace  was,  as  it  was  imagined, 
inevitably  distributed  over  the  boiler  surfaces.  Qualitative 
experiments  were  made  by  Robert  Stephenson,  Mr.  Edward 
Woods,  Mr.  Dewrance,  and  others,  including  Mr.  C.  Wye 
Williams,  a  good  account  of  which  will  be  found  in  Mr.  D.  K. 
Clark's  work  on  "The  Steam  Engine"  (Vol.  i.  pp.  75-81).  In 
general  they  all  bore  witness  to  a  much  more  active  evaporation 


142 


THE  PRACTICAL  PHYSICS  OF 


at  the  fire-box  end  of  the  boiler,  which  result  was  as  generally 
ascribed  solely  to  the  action  of  radiant  heat. 

Graham's  Experiments. — Mr.  John  Graham  published  in  the 
Memoirs  of  the  Literary  and  Philosophical  Society  of  Man- 
chester 1  the  record  of  some  careful  experiments  on  the  evapora- 
tive functions  of  steam  boilers,  which  he  had  carried  out  in 
1858.  In  the  course  of  these  he  endeavoured  to  ascertain  the 
proportion  of  the  total  evaporation  which  was  due  to  different 
portions  in  the  length  of  a  cylindrical  boiler,  by  dividing  the 
boiler  into  sections  of  3  ft.  long,  as  in  Fig.  67.  The  three  cylinders 
were  of  plate  J  in.  thick,  3  ft.  diameter,  and  3  ft.  long.  They  were 
placed  end  to  end  on  a  brick  setting,  so  as  to  form  practically  a 
boiler  of  9  ft.  long.  A  grate  3  ft.  long  and  2  ft.  wide  was 
placed  9^  in.  below  the  first  section,  with  a  concentric  flue  of 


FIG.  67. 

4  in.  radial  width,  extending  under  the  two  succeeding  cylinders, 
and  carried  up  on  each  side  to  the  level  of  their  centres.  The 
fire  bars  were  ^  in.  thick,  with  ^  in.  air  spaces,  and  the  grate 
area  was  6  sq.  ft.  The  heating  surface  of  the  sections  in  their 
order  from  the  grate  end  was  10-53,  I4'I3  and  14' 1 3  sq.  ft. 
respectively,  making  a  total  of  38-79  sq.  ft.  This  is  practically 
the  same  extent  of  heating  surface  as  in  the  evaporator  used  in 
Mr.  Lang's  experiments,  but  no  further  comparison  between 
them  is  possible,  because  the  surface  in  Mr.  Graham's  boiler 
was  so  badly  disposed  for  utilisation  of  the  heat.  The  only  point 
of  interest  in  the  results  is  that  of  the  proportion  of  the  total 
evaporation  which  is  due  to  the  various  sections.  The  averages 
of  numerous  experiments  showed  that  if  the  evaporation  of  the 
first  were  taken  as  100,  the  second  and  third  sections  were 
represented  by  39-3  and  17-1  respectively. 

1  Vol.  xv.  (1860),  page  8. 


THE  MODERN  STEAM  BOILER. 


A  similar  result  was  obtained  in  one  series  of  Mr.  Wye 
Williams'  experiments,  where  he  used  a  6  ft.  boiler  and  a  2  ft. 
boiler  in  different  positions.  When  the  2  ft.  boiler  was  placed 
second  in  the  course  of  the  hot  gases  from  fire  to  chimney,  it 
evaporated  only  80  Ibs.  and  86  Ibs.  of  water  per  hour,  but  when 
placed  first  it  evaporated  417  Ibs.  per  hour. 

Northern  Railway  of  France  Experiments. — Th,e  most  elaborate 
and  useful  experiments  carried  out  on  this  part  of  our  subject 
were  undoubtedly  those  of  the  engineers  of  the  Chemin  de  Fer 
du  Nord  (Northern  Railway  of  France).  The  records  of  these 
experiments  are  found  in  writings  of  M.  C.  Couche1  and  M.  Paul 
Havrez,2  and  in  English  in  "  The  Steam  Engine,"  by  Mr.  D.  K. 
Clark. 


FIG.  68. 


The  boiler  of  a  small  goods  engine  was  prepared  for  these 
experiments  by  being  separated  into  five  sections  by  the  insertion 
of  tube  plates  (see  Fig.  68),  the  fire-box,  with  a  small  length  of 
tubes  (3^  in.),  forming  the  first  section.  "  The  fire-box  was  3  ft. 
square,  presenting  a  grate  area  of  9  sq.  ft.,  and  a  heating  surface 
of  60-28  sq.  ft.  There  were  125  tubes,  12  ft.  4  in.  long,  and  about 
if  in.  in  diameter.  The  barrel  of  the  boiler  with  the  tubes  was 
divided  into  four  sections,  each  3-01  ft.  in  length.  Each  section, 
together  with  the  fire-box  portion,  was  closed  at  the  ends  by 
tube  plates  and  made  steam-tight,  to  be  tried  under  steam  of  the 

1  Chemins  de  Fer,  voie  et  material  roulant,  by  M.  C.  Couche,  1876,  Vol.  iii., 
p.  32.  Paris,  Dunod. 

*  Annals  du  Genie  Civil,  1874,  p.  521  ;  also  Min.  Proc.  Inst.  C.E.,  Vol.  xxxix., 
1875,  P-  398,  and  "  The  Steam  Engine,"  by  D.  K.  Clark,  Vol.  i.,  pp.  84—90. 


144  THE  PRACTICAL  PHYSICS  OF 

ordinary  working  pressure.  The  draught  was  excited  by  a  blast 
of  steam  from  another  boiler."  "The  fire-box  section  contained 
1 6  cubic  ft.  of  water,  and  each  tubular  section  held  11-3  cubic  ft. 
Each  section  was  fed  from  a  gauged  tank  by  a  special  donkey- 
pump,  and  the  water  levels  were  maintained  strictly  uniform. 
Each  section  was  fitted  with  a  steam  chest,  a  pressure  gauge, 
and  a  safety  valve.  The  conditions  of  the  trials  were  varied  by 
plugging  half  the  number  of  tubes."  The  heating  surface  was 
as  follows  : — 

Tubes  all  Half  tubes 

Heating  surface.  open.  closed. 

ist  section  (fire  box  60*28,  tubes  16-15)     76-43  sq.  ft.  65-9  sq.  ft. 

2nd      „  .-. 179  „  89-5       „ 

3rd      „  ...   179  „  89-5      „ 

4th      „  ...   179  „  89-5      „ 

5th      „  179  „  89-5      „ 


Total  surface  ...792-43      „      423-9      „ 

The  total  heating  surface  is  equal  to  88  times  the  fire-grate 
area. 

The  results  of  three  series  of  these  most  interesting  trials  are 
given  in  the  following  Table.  In  the  first  and  second  series, 
coke  and  briquettes  were  the  fuels  used,  and  in  the  third  series, 
with  briquettes  for  fuel,  half  the  tubes  were  closed  by  being 
plugged  at  the  fire-box  end.  The  force  of  draught  was  gradually 
increased  in  each  series  from  20  to  100  millimetres  of  water, 
measured  in  the  smoke  box.  In  regular  work,  the  vacuum  varied 
from  20  to  80  millimetres,  or  from  about  f  inch  to  3!  ins. 

From  the  Table,  it  will  be  seen  that  "  from  two-fifths  to  one- 
half  of  the  whole  quantity  of  water  was  evaporated  from  the 
surface  of  the  fire-box  section,  although  this  surface  was  less 
than  one-tenth  of  the  whole  heating  surface.  Per  square  foot  of 
the  respective  surfaces,  the  evaporation  from  the  fire-box  section 
amounted  to  from  two  to  three  times  that  of  the  first  section  of 
tube  surface."  The  figures  of  quantity  of  water  evaporated  per 
square  foot  of  heating  surface  in  columns  7,  9,  n,  13,  and  15, 
also  show  rates  of  from  20  to  44-7  Ibs.  obtained  in  the  first 
section,  with  immediate  falling  off  in  the  second  and  following 
sections,  whilst  the  evaporation  from  the  boiler  as  a  whole — per 
square  foot  of  heating  surface — varied  from  4'i8  to  16-20  Ibs, 


THE  MODERN  STEAM  BOILER. 


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146  THE  PRACTICAL  PHYSICS  OF 

The  important  fact  is  that  a  rate  of  evaporation  amounting  to 
nearly  50  Ibs.  of  water  per  square  foot  of  heating  surface  was 
obtained  from  a  part  of  a  boiler — and  if  from  a  part,  why  not 
from  a  whole  boiler  ?  Moreover,  the  Table  conveys  the  signifi- 
cant fact  that  the  rate  of  evaporation  was  greatly  affected  by 
the  velocity  of  movement  of  the  hot  gases,  as  indicated  by 
the  varying  force  of  draught  used  and  the  area  of  the  flue 
tubes. 

Thus,  with  briquettes  for  fuel,  and  all  the  flue  tubes  open,  the 
figures  were: — 

Force  of  draught — millimetres        20        40        60        80      100 
Evaporation  in  ist  section,  Ibs. 

per  sq.  ft.  of  surface  ...  23*5  307  38*2  42-9  38-9 
whilst  with  the  same  fuel  and  half  the  flue  tubes  closed,  the 
figures  for  evaporation  were,  for  the  same  draught  pressure — 

26-5     30-1     39-6     43-6    447. 

The  effect  of  reducing  the  flue-tube  area  by  one  half  for  trie 
same  draught  pressures,  would  be  to  cause  a  more  rapid  rate  of 
movement  over  the  heating  surface,  and  in  those  tubes  which 
were  open,  and  hence  the  evaporation  in  all  the  sections  of  the 
boilers  was  increased  in  the  trial  made  under  these  conditions. 
The  above  are  the  figures  for  the  first  section  of  the  boiler,  but 
the  evaporation  in  the  other  sections  was  increased  in  greater 
proportion. 

Fig.  69  shows  in  a  graphic  manner  the  distribution  of  heat 
in  the  various  sections  of  the  boiler. 

Hirsch's  Experiments. — Some  similar  phenomena  were  shown 
in  the  results  of  experiments  carried  out  by  M.  J.  Hirsch,1  at  the 
Conservatoire  des  Arts  et  Metiers,  at  Paris — perhaps  the  most 
important  as  yet  published.  These  experiments  were  divided 
into  three  parts,  comprising  :— 

:^I.  Investigation  of  the  rate  of  evaporation  in  the  part  of  a 
boiler  most  exposed  to  the  heat  of  the  fire  and  liable  to  over- 
heating ; 

II.  Experiments  on  the  transmission  of  heat  through  metal 
plates,  from  flame  on  one  side  to  water  on  the  other  ;  and 

1  Published  in  Annales  du  Conservatoire  des  Arts  et  Metiers,  Paris, 
2nd  series  Vol.  i.,  and  in  Bulletin  de  la  Societe  d'encouragement  pour 
1'Industrie  Nationale,  '4th  Ser.,  Tome  v.  (May,  1890),  p.  302  ;  also  Abs.  in  Min. 
Proc.,  InsL;  C.E.,  Vol.;  cviii.,  p.  464. 


THE  MODERN  STEAM  BOILER. 


III.  A  special  study  of 
the  effects  of  a  coating  of 
oil  or  grease  on  the  con- 
ductivity of  the  coated 
surface. 

I.  Evaporation.  —  In 
connection  with  the  first 
part,  M.  Hirsch  rightly 
pointed  out  that  the 
figures  usually  given  to 
express  the  rate  of  evapo- 
ration in  boilers  per 
square  metre  (or  per 
square  foot)  of  heating 
surface,  are  only  averages 
obtained  by  dividing  the 
total  evaporation  by  the 
total  area  of  surface  ex- 
posed to  the  action  of 
heat.  They  do  not  afford 
any  idea  of  the  actual 
intensity  of  evaporation 
at  any  one  point,  and  yet 
it  is  well  known  that  in 
the  neighbourhood  of  the 
fire  the  rate  of  evapora- 
tion must  be  much  greater 
than  at  other  points  far- 
ther removed  from  it.  In 
no  boilers  hitherto  made 
is  there  anything  like  a 
uniform  rate  of  evapora- 
tion at  all  parts  of  the 
surface.  Consequently, 
it  becomes  important  to 
learn  what  is  the  maxi- 
mum rate  in  those  parts 
which  are  more  directly 
subject  to  the  action  of 
the  fire. 


FIG.  69. 


148 


THE  PRACTICAL  PHYSICS  OF 


With  a  view  to  ascertain  this,  M.  Hirsch  took  a  cylindrical 
boiler  10  ft.  long  and  2  ft.  2  ins.  diameter,  with  heating  surface 
amounting  to  35 J  sq.  ft.  There  were  horizontal  feed-heaters 
added,  with  a  surface  of  107^  sq.  ft.,  so  that  boiler  and  feed- 
heater  together  had  a  total  heating  surface  of  142!  sq.  ft..  The 
grate  area  was  3-85  sq.  ft.  and  a  blower  was  applied  for  the 
higher  rates  of  combustion.  A  small  portion  of  the  surface  of  the 
boiler,  directly  over  the  lire,  just  in  front  of  the  bridge,  was 
isolated  by  means  of  a  vertical  tube  being  bolted  to  the  plates,  a 
joint  being  made  with  asbestos  and  india  rubber.  The  tube  was 
of  copper,  4  ins.  diameter,  and  extended  above  the  water  level  in 


the  boiler,  with  a  cover  to  prevent  its  liquid  contents  being  pro- 
jected out  of  the  tube,  whilst  the  steam  generated  in  it  could 
escape  into  the  steam  space.  The  heating  surface  of  the  tube  was 
19*3  sq.  ins.,1  and  it  was  separately  supplied  with  water,  which 
was  maintained  at  the  same  level  as  in  the  boiler.  Previous  to 
an  experiment,  the  boiler  was  heated  for  several  hours  and  com- 
munication was  then  cut  off  between  it  and  the  experimental 
tube.  During  the  trials  the  steam  pressure  was  kept  at  about 
60  Ibs.  per  sq.  in. 

The   arrangement    of   the   apparatus    is   shown    in    Figs.  70, 

1  How  this  was  arrived  at  does  not  appear  in  the  paper,  as  the  tube  was 
heated  entirely  through  the  plate  at  its  bottom  end,  and  therefore  the  area 
of  heating  surface  should  apparently  be  12-566  sq.  ins.,  or  a  fraction  over  that. 


THfc  MODERN  STEAM  BOILER. 


149 


71,  and  72,  in  which  A  is  the  cylindrical  boiler,  C  the  grate, 
D  the  bridge,  F  the  flues,  L  the  safety  valve,  S  the  man-hole, 
T  the  experimental  tube,  and  N  the  water  gauge  ;  B  B  are  the 
feed-heaters.  In  M.  Hirsch's  paper,  the  results  of  the  experi- 
ments are  tabulated,  showing  the  total  consumption  of  coal 
or  coke  and  of  water  ;  the  consumption  of  fuel  in  kilogrammes 
per  square  metre  of  grate  surface  per  hour,  and  the  evaporation 
of  water  in  litres  per  square  metre  of  heating  surface  per  hour 
(i)  in  the  cylindrical  boiler  alone,  (2)  with  the  feed-heaters 
added,  and  (3)  in  the  experimental  tube. 

With  different  degrees  of  force  of  draught  and  intensity  of 


FIG.   71. 


FIG.   72. 


tire,  the  consumption  of  fuel  per  hour  per  square  foot  of  grate 
varied  from  16  Ibs.  to  48  Ibs.  M.  Hirsch  remarked  that  in 
general  the  evaporation  in  stationary  boilers  of  this  form  ranges 
from  1-6  to  2-4  Ibs.  of  water  per  hour  per  square  foot  of  heating 
surface.  In  this  boiler  under  (i),  it  ranged  from  9*5  to  20  Ibs. 
per  square  foot  of  surface  per  hour  ;  under  (2),  from  2*4  to 
5-2  Ibs.  ;  but  under  (3),  in  the  tube  covering  the  highly  heated 
portion  of  surface,  the  rate  of  evaporation  was  from  21  Ibs.  to 
50  Ibs.  per  square  foot  per  hour. 

This  is  undoubtedly  a  good  result,  but  it  will  be  apparent,  on 

examination  of  the  sectional  elevation  of  the  boiler  and  tube, 

h  at  the  experimental  tube  was  of  such  a  limited  size  and  was 


ISO  THE  PRACTICAL  PHYSICS  OF 

so  arranged  as  to  present  great  difficulties  in  the  way  of  the 
proper  circulation  of  the  water  in  it,  and  consequently,  that  even 
a  better  evaporative  result  might  have  been  obtained  with 
a  better  arrangement.  The  heating  took  place  only  at  one  end 
of  the  tube,  because  when  the  water  was  boiling  in  both  tube 
and  boiler  there  could  be  no  heating  through  the  sides  of  the 
tube,  all  being  at  the  same  temperature,  and  all  the  circulation 
possible  was  that  which  could  take  place  within  the  limits  of  the 
tube,  the  upward  and  downward  currents  having  each  to  find 
a  passage  for  itself.  At  the  rate  of  evaporation  noted,  it  is 
probable  that  the  circulation  could  only  have  been  pulsatory, 
the  water  finding  its  way  down  after  each  outburst  of  steam. 
Under  the  circumstances  described  it  is  remarkable  that  so  high 
a  rate  of  evaporation  was  attained.  The  presence  of  a  con- 
centric tube,  or  of  some  form  of  diaphragm  to  direct  the  currents, 
would  in  all  probability  have  improved  the  result. 

II.  Heat  Transmission. — In  dealing  with  the  conditions  under 
which  transmission  of  heat  takes  place,  M.  Hirsch  adopted 
the  division  of  the  subject  usual  since  Fourier,  and  considered 
(i)  the  exterior  conductivity  from  hot  gases  to  metal,  (2)  the 
interior  conductivity  of  the  metal  itself,  and  (3)  the  exterior 
conductivity  from  iron  to  water.  It  is  in  the  first  division 
that  the  greatest  losses  of  heat  have  taken  place  almost 
universally  hitherto  in  boiler  practice,  although  mal-arrange- 
ment  may,  and  no  doubt  often  does,  give  a  bad  result 
in  the  third  division  also.  The  interior  conduction  in 
a  homogeneous  metal  is  nearly  constant,  and  once  the 
permanent  state  of  affairs  between  the  two  faces  is  established, 
the  temperature  varies  with  the  distance  between  them  according 
to  an  arithmetical  progression,  and  the  quantity  of  heat  which 
traverses  the  plate  is  proportional  to  the  difference  between  the 
temperatures  of  t\vo  points  situated  at  infinitely  small  distances 
from  the  two  faces. 

As  to  exterior  conduction,  or  the  property  in  virtue  of  which 
exchanges  of  heat  take  place  between  metal  and  fluids  bathing 
its  surfaces,  the  laws  which  govern  these  exchanges  are,  as 
M.  Hirsch  remarked,  not  well  understood,  but  it  is  certain  that, 
all  things  being  equal,  the  rate  of  transmission  increases  when 
the  difference  of  temperature  between  the  metal  and  the  fluid 
in  contact  with  it  becomes  greater. 


THE  MODERN  STEAM  BOILER.  151 

It  is  also  certain  that  this  transmission  is  influenced  by  the  con- 
dition of  the  surface  of  the  metal,  by  the  movement  of  the  fluids, 
etc.  The  transmission  of  heat  through  the  metal  and  also  from 
the  metal  to  the  water  takes 'place  very  readily,  so  that  with  a 
very  small  difference  between  the  temperature  of  the  iron  and 
that  of  the  water,  heat  passes  in  large  quantities  freely — always 
provided  that  there  are  no  thick  incrustations  or  coatings  of  oily 
matters.  The  communication  of  heat  from  a  liquid  is  much 
more  active  than  from  a  gas,  so  that  the  face  next  the  water  is 


never  much  higher  in  temperature  than  the  water,  whilst  the  other 
face  is  at  a  much  lower  temperature  than  that  of  the  hot  gases. 

In  investigating  these  matters,  M.  Hirsch  employed  the 
arrangement  of  apparatus  shown  in  Figs.  73,  74,  and  75,  con- 
sisting of  a  circular  disc  of  fine  boiler  plate,  A  A,  10  millimetres 
(about  £  in.)  thick,  and  40  millimetres  (or  157  ins.)  diameter, 
machined  on  both  surfaces.  A  cylinder  of  copper,  H  H,  bolted 
to  the  plate  at  its  outside  circumference,  formed  a  small  boiler 
or  cylindrical  dish  for  the  water,  and  this  was  surmounted  by 
a  conical  top,  K  K,  and  surrounded  by  a  complete  casing,  L  L, 
leaving  a  space,  around  the  cylinder  and  over  the  conical  cover, 


THE  PRACTICAL  PHYSICS  OF 


into  which  the  steam  was  allowed  to  escape,  so  that  there  should 
be  as  little  priming  water  carried  away  as  possible.     A  furnace 


FIG.   74. 


was  formed  of  a  crucible,  B  B,  of  fireclay  pierced  at  C  by  a  pipe 
E,  which  conducted  the  gas  and  air  under  pressure  to  give  a 


blow-pipe  iiame.     A  casing,  D  D,  surmounted  the  crucible,  and 
the  flame  striking  upwards  on  the  plate  A,  passed  over  the  top 


THE  MODERN  STEAM  BOILER. 


153 


of  the  crucible  and  descended  inside  the  casing  D  and  out  at  6. 
The  evaporation  of  water  was  reckoned  as  being  that  from  the 
area  of  plate  comprised  within  the  cylinder  casing  D  D  (16 
millimetres  diameter  ;  6|  ins.). 

Apparatus  for  regulating  the  supply  of  water  and  maintaining 
a  constant  level  was  provided,  and  on  the  under  surface  of  the 
plate,  in  the  zone  of  heating,  M.  Hirsch  introduced  a  number  of 
fusible  plugs  of  alloys  having  different  melting  points.  These 
were  disposed  in  two  concentric  circles  (one  2f  in.  diameter  and 
the  other  4!  ins.  diameter)  in  such  a  way  that  two  plugs  having 
the  same  melting  point  were  placed  one  in  the  inner  circle  and 
the  other  at  the  opposite  point  in  the  outer  circle.  This  pre- 
caution was  taken  to  guard  as  much  as  possible  against  the 
effects  of  local  inequalities  of  heating.  Fig.  75  shows  the 
arrangement. 

IN     THE     IN'XER     CIRCLE. 

Lead.      Zinc. 

Nos.  of  the  plugs      ...       i  2          3  4  5        6         7         8        9          10      ir      12 

MeltingtemperaturesC.no0    121°     128°      143°     150°   170°   187°!     220°  250°  335°  335°  450° 
F.  230°   249-8°   262-4°  289.4°  302°  338°  368-6°  428°  482°  635°  635°   842° 

IN     THE     OUTER     CIRCLE. 

Nos.  of  the  plugs   ...   13   14    15   16   17   18   19   20   21    22    23   24 
Melting  points      C.  170°  187°   220°  250°  335°  335°  450°  no0  121°   128°   143°   150° 
F.  338°  368-6°  428°  482°  635°  635°  842°  230°  249-8°  262-4°  289-4°  3°2° 

The  range  was  thus  from  230°  F.  to  lead  at  635°  F.,  and  zinc 
at  842°  F. 

M.  Hirsch's  first  experiments  were  made  with  distilled  water 
and  a  clean  plate.  In  an  experiment  made  on  August  23rd,  1887, 
the  temperature  of  the  plate,  as  indicated  by  the  fusible  plugs, 
melted  and  intact,  was  between  338°  F.  and  369°  F.,  and  water 
was  evaporated  at  the  rate  of  29^59  Ibs.  per  hour  per  square  foot 
of  heating  surface.  This  result  was  plotted  in  a  diagram,  Fig.  76, 
and  was  reproduced  with  a  number  of  those  most  regularly 
carried  out  in  another  diagram,  Fig.  77,  in  which  the  abscissae 
represent  the  quantity  of  water  evaporated  per  unit  of  surface  per 
hour,  and  the  ordinates  the  temperatures  of  the  plate.  Two  lines, 
A  A  and  B  B,  are  traced  on  the  diagram,  showing  the  variations  of 
temperature  of  the  inner  and  outer  circles  of  plugs  as  compared 
with  the  amount  of  water  evaporated,  and  a  third  line,  C  C,  gives 
a  mean  of  these  variations.  M.  Hirsch  concluded  from  his 
various  experiments  that  the  temperature  of  the  surface  of  the 
plate  was  never  uniform  throughout ;  lit  was  hotter  at  the  inner 


154  THE  PRACTICAL  PHYSICS  OF 

circle  of  plugs,  where  the  flame  had  more  direct  action,  than 
at  the  outer  circle,  the  difference  being   about   29°  F.      The 


temperature  of  the  surface  exposed  to  the  fire  rises  progressively 
with  the  increase  of  the  quantity  of  heat  transmitted  through  the 


O 

210     260' 


lOOKj 


FIG.   77. 


plate.     To  read  the   phenomena   aright,  however,  we   should, 
according    to    M.   Hirsch    consider   rather    the    excess    of   the 


THE  MODERN  STEAM  BOILER.  155 

temperature  of  the  plate  over  that  of  the  water,  which  was 
constant  at  212°  F.  He  thus  found  that,  with  an  evaporation  of 
20  Ibs.  per  square  foot  per  hour,  the  difference  of  temperature 
was  167°  F.  ;  it  was  nearly  212°  F.  for  an  evaporation  of  40  Ibs. 
per  square  foot,  but  it  would  not  reach  302°  F.  (according  to 
line  B  B  on  diagram  Fig.  77)  until  an  evaporation  was  obtained 
of  75  Ibs.  per  square  foot  per  hour. 

If  the  temperature  of  the  water  rises  in  any  boiler,  this 
difference  between  plate  and  water  does  not  increase  in 
proportion.  Thus,  for  instance,  if  we  have  an  iron  firebox  with 
plates  of  f  in.  thickness,  supplied  with  water  at  a  temperature  of 
356°  F.  (there  being  an  effective  pressure  of  8*5  kilogrammes  per 
metre  carre  =  10  atmospheres  or  146  Ibs.  per  square  inch),  and 
evaporating  40  Ibs.  of  cold  water  per  hour  per  square  foot,  the 
corresponding  difference  of  temperature  should  be  212°  F.,  but 
the  temperature  of  the  iron  plate  never  reaches  568°  F. 

It  is  well  known  that  if  a  small  boiler  be  made  of  paper  and 
held  over  the  flame  of  a  candle,  the  water  will  boil  but  the  paper 
will  not  be  burned.  M.  Hirsch  repeated  this  experiment  in 
various  forms,  using  the  flame  of  a  large  Bunsen  burner  and  that 
of  a  blow-pipe  used  in  enamelling,  which  melted  glass  in  a  few 
moments,  but  the  result  was  always  the  same.  The  paper  would 
burn  doxvn  to  the  level  of  the  water  and  a  sheet  of  paper  placed 
over  the  flame  in  contact  with  the  bottom  of  the  boiler  would 
instantly  be  burned  up,  but  the  boiler  itself  when  containing 
water  was  never  attacked  by  the  flame. 

These  various  facts  and  figures  satisfied  M.  Hirsch  that  there 
is  no  danger  of  overheating  the  metal  plates  of  boilers,  whatever 
may  be  the  activity  of  evaporation,  if  the  metal  be  sound  and  in 
direct  contact  with  the  water. 

There  are,  however,  other  conditions  which  may  intervene  to 
check  the  transmission  of  the  heat,  and  these  may  be  found 
either  in  the  metal  itself  or  interposed  between  the  metal  and 
the  water.  Consequently,  M.  Hirsch  carried  out  other  experi- 
ments in  order  to  study  these  conditions. 

Effects  of  Increased  Viscosity  of  Water. — The  effects  of  water  of 
increased  viscosity  were  imitated  by  mixing  starch  with  the 
water,  in  proportions  successively  of  0*2  per  cent,  and  0*5  per 
cent,  of  the  weight  of  water  used.  With  the  smaller  proportion 
the  temperature  difference  was  raised  only  about  15°  C.  (or 


156  THE  PRACTICAL  PHYSICS  OF 

59°  F.)  above  that  which  was  registered  with  distilled  water 
alone.  Although  the  water  mixed  with  0-5  per  cent,  of  starch 
was  certainly  more  viscous,  the  line  of  temperature  appeared  not 
to  be  elevated  to  any  serious  extent. 

M.  Hirsch  points  out  that  this  latter  proportion  of  starch  is 
rarely  if  ever  reached,  even  when  amylaceous  materials  are  used 
to  prevent  the  formation  of  incrustations,  but  that  even  to  that 
limit  they  do  not  present  any  great  inconvenience  or  danger  of 
overheating. 

Effects  of  Incrustations. — The  conditions  of  boilers  having 
incrustations  of  various  thicknesses  were  then  imitated  by  means 
of  layers  of  plaster  put  on  the  interior  surface  of  the  plate.  With 
a  layer  of  plaster  2Vth  inch  thick  it  was  necessary  to  employ  a 
comparatively  gentle  degree  of  heat  to  prevent  cracking  of  the 
layer,  'so  that  the  experiment  did  not  go  beyond  a  rate  of 
evaporation  of  39  Ibs.  per  hour  per  square  foot  of  surface.  The 
temperature  difference  was  found  to  be  about  30°  C.  v'or  86°  F., 
higher  than  when  distilled  water  was  in  direct  contact  with  the 
plate. 

With  a  layer  of  plaster  of  fgths  inch  thickness,  to  evaporate 
30  Ibs.  of  water  caused  the  external  temperature  of  the  plate  to 
rise  above  482°  F.  and  to  evaporate  40  Ibs.  it  exceeded  752°  F., 
these  results  being  75°  F.  and  410°  F.  respectively  above  those 
obtained  with  water  in  immediate  contact  with  the  plate. 

With  this  thickness  of  plaster  an  evaporative  rate  of  44  Ibs. 
was  reached,  but  the  plaster  then  cracked  and  separated  from 
the  plate. 

Effects  of  Flaws  and  Joints. — The  effects  of  Haws  in  the 
substance  of  the  metal,  and  of  joints,  upon  the  passage  of  the 
heat,  were  ascertained  in  a  very  ingenious  manner.  In  a  joint  or 
seam,  the  two  parts  of  the  metal  are  brought  together  as  closely 
as  possible,  and  it  is  mainly  the  additional  thickness  which  is 
objectionable — the  continuity  of  the  metal  for  heat  conduction 
is  but  little  interfered  with.  In  the  case  of  a  flaw,  on  the  other 
hand,  the  parts  of  the  metal  are  kept  apart  by  a  small  layer  of 
foreign  matter.  The  joint  was  imitated  as  follows  :  Upon  the 
face  of  the  plate  touching  the  water  a  sheet  of  steel  Voths  inch 
thick,  carefully  planed  and  ritted,  was  placed,  care  being  taken 
that  both  were  in  contact  at  all  parts  of  their  surfaces.  A  sheet 
of  tinfoil  was  laid  between  them  and  when  the  plates  were 


THE  MODERN  STEAM  BOILER.  157 

heated  and  the  tin  melted,  the  two  plates  were  then  drawn 
tightly  together  by  bolts,  so  that  a  part  of  the  melted  tin  was 
expelled  and  a  perfect  soldered  joint  made. 

Evaporative  experiments  carried  out  with  the  plate  in  that 
condition  showed  that  the  temperature  line  in  the  diagram  was 
almost  parallel  to  that  obtained  with  the  single  boiler  plate, 
except  when  the  rate  of  evaporation  was  high.  The  discrepancy 
which  for  an  evaporation  of  100  kilogrammes  per  square  metre, 
or  20  Ibs.  per  square  foot  per  hour,  was  about  50°  C.  (or  122°  F.), 
reached  70°  C.  (or  158°  F.)  for  an  evaporation  of  300  kilogrammes, 
or  60  Ibs.  per  square  foot.  At  this  latter  point  the  temperature 
of  the  surface  of  the  plate  exposed  to  the  fire  was  more  than 
392°  F.  above  that  of  the  water. 

Flaws  in  the  metal  were  imitated  by  strewing  the  interior 
surface  of  the  plate  with  finely-powdered  talc,  and  then  affixing 
the  sheet  of  steel  to  the  plate  by  means  of  bolts  screwed  up  till 
a  distance  of  only  -,y-J-0th  inch  separated  the  two.  When  the 
boiler  was  then  filled  with  distilled  water  and  put  in  action, 
with  an  evaporation  of  3olbs.  per  hour  per  square  foot  of  heating 
surface,  the  temperature  of  the  plate  exceeded  662°  F.,  being 
270°  in  excess  of  that  which  it  had  acquired  when  in  direct 
contact  with  the  water.  With  an  evaporation  of  50  Ibs.  all  the 
plugs,  even  those  of  zinc,  melted,  showing  that  the  temperature 
of  the  surface  exceeded  842°  F.,  and  the  plate  was  in  great 
danger  of  being  overheated.  Such  would  be  the  effects  of  flaws 
in  that  part  of  the  metal  exposed  to  the  fire. 

Effects  of  Contact  ivith  Hot  Brickwork. —  In  order  to  ascertain  if 
the  idea  were  correct  that  the  plates  of  boilers  could  be  over- 
heated by  contact  with  incandescent  brickwork,  M.  Hirsch  filled 
his  furnace  with  pieces  of  fire-brick,  leaving  free  passage  for  the 
flame  between  them,  so  that  the  plate  of  his  experimental 
evaporating  dish  would  rest  on  them  when  in  position  for  work. 
The  results  of  this  experiment  were,  an  evaporation  of  35  Ibs.  of 
cold  wrater  per  hour  per  square  foot  of  heating  surface,  the 
fusible  flugs,  Nos.  7  and  14  (368-6°  F.)  having  melted,  and  those 
of  Nos.  8  and  15  (428°  F.)  remaining  intact.  These  were  pre- 
cisely the  results  obtained  in  the  first  experiments  with  distilled 
water  under  normal  conditions  of  the  apparatus,  and  show  that 
the  presence  of  the  firebricks  does  not  influence  the  transmission 
of  the  heat. 


I5g  THE  PRACTICAL  PHYSICS  OF 

In  Fig.  78  all  the  various  mean  temperature  lines  are 
assembled  in  one  diagram  for  the  purpose  of  comparison. 
Referring  to  the  first  part  of  his  researches,  M.  Hirsch  noted 
that  the  evaporation  in  ordinary  cylindrical  land  boilers,  as  used 
for  manufacturing  purposes,  does  not  exceed,  at  the  part 
directly  exposed  to  the  fire,  20  to  28  Ibs.  per  hour  per  square 


aon 


FIG.  78. 


foot  of  heating  surface,  and  that  it  was  improbable  that  the  rate 
could  go  with  such  boilers  to  51  Ibs.  per  square  foot,  even  with 
the  strongest  fire.  The  temperature  lines  in  these  diagrams 
showed,  however,  that  dangerous  differences  of  temperature 
between  metal  and  water  need  not  be  expected  short  of  an 
evaporation  of 'from  80  to  102  Ibs.  per  square  foot  per  hour. 


THE  MODERN  STEAM  BOILER.  159 

III.  Effects  of  Oil  and  Grease. — In  this  portion  of  his  experi- 
ments, M.  Hirsch  led  the  van  in  inquiring  into  the  effects 
which  the  presence  of  oil  and  grease  upon  the  surface  of  iron 
plates  had  on  the  transmission  of  heat.  In  the  experiments 
just  described,  he  was  decidedly  in  advance  of  all  previous 
inquirers  in  his  attempt  to  measure  the  actual  temperature  of 
the  iron  of  boilers  by  means  of  fusible  plugs. 

In  this  last  division  he  commenced  by  covering  the  interior 
surface  of  the  plate  with  mineral  oil,  which  was  then  wiped  off, 
and  left  a  greasy  layer  of  no  appreciable  thickness,  but  sufficient 
to  prevent  the  adherence  of  the  water  to  the  iron.  The  boiler 
was  filled  up  with  distilled  water,  and  the  experiment  conducted 
as  in  previous  instances.  It  was  found  that  even  when  the 
heating  was  kept  moderate,  the  exterior  surface  of  the  plate 
reached  temperatures  notably  higher  than  was  the  case  when 
the  water  came  into  direct  contact  with  the  interior  surface. 
With  a  strong  flame  peculiar  phenomena  were  observed.  In 
certain  cases  the  increase  of  temperature  coincided  with  the 
increased  intensity  of  the  fire.  The  difference  between  the 
temperature  of  the  water  and  that  of  the  exterior  surface  of  the 
plate  was  (50°  C.),  122°  F.  higher  than  in  the  experiments  with 
pure  water,  with  an  evaporation  of  30  Ibs.  per  hour  per  square 
foot  of  heating  surface.  With  an  evaporation  of  50  Ibs  it  was 
(80°  C)  176°  F.  higher,  and  the  temperature  of  the  flame  surface 
was  (200°  C.)  392°  F.  above  that  of  the  water.  In  other  cases 
the  results  were  entirely  different  ;  even  after  moderate  heating, 
and  an  evaporation  of  only  35  Ibs.,  all  the  fusible  plugs  were 
found  melted,  which  was  held  to  prove  that  the  temperature  of 
the  plate  had  been  above  842°  F.  for  the  major  part  of  its 
thickness.  The  effects  of  oiling  the  inner  surface  of  a  boiler 
may  thus  be  manifested  in  two  different  ways  ;  either  in  a 
moderate  increase  in  the  temperature  of  the  heated  surface,  or 
with  a  fire  of  ordinary  intensity  the  metal  becomes  heated  to  a 
very  high  degree. 

Qualitative  Experiments.  Effects  of  Grease. — In  order  to  observe 
further  the  effects  produced  by  oily  materials,  M.  Hirsch  aban- 
doned his  special  quantitative  apparatus  and  used  some  small 
tinned  saucepans,  placed  on  his  crucible-shaped  furnace,  for 
some  qualitative  experiments.  He  had  observed  that  where 
an  abnormal  elevation  of  temperature  was  attained  in  the 


160  THE  PRACTICAL  PHYSICS  OF 

experiments,  black  patches,  apparently  arising  from  the  partial 
decomposition  of  fatty  matter,  adhered  to  the  boiler  at  the 
beginning  of  the  trial,  not  having  been  completely  removed  by 
the  cleansing.  Wishing  to  discover  if  they  had  any  influence  on 
the  phenomena  of  the  transmission  of  heat,  he  greased  a  clean 
tinned  saucepan  with  mineral  lubricating  oil  (oleonaphte)  and 
heated  it  without  water  over  a  slow  fire  to  decompose  the  fatty 
matter.  The  bottom  of  the  saucepan  wras  found  to  be  covered 
with  a  black  coating  to  which  water  would  not  adhere.  The 
saucepan  was  then  filled  with  water,  and  heated  over  the 
furnace.  After  boiling  a  minute  one  part  at  the  bottom  of  the 
saucepan  was  seen  to  become  red  hot,  and  the  incandescence 
soon  spread  over  the  rest  of  the  area  covering  the  opening  of 
the  furnace.  Evidently  the  bottom  of  the  saucepan  \vas  never 
wetted,  and  the  water  assumed  the  spheroidal  condition.  Even 
if  the  grease  was  confined  to  a  limited  portion  of  the  bottom, 
that  part  alone  became  incandescent  at  first,  but  the  red  heat 
gradually  extended  over  all  the  surface  exposed  to  the  fire. 
This  experiment  was  repeated  several  times  with  different 
intensities  of  fire.  With  heat  corresponding  to  an  evaporation  of 
about  54  Ibs.  per  hour  per  square  foot  of  heating  surface,  the 
colour  of  the  bottom  was  bright  orange,  but  when  30  Ibs.  were 
evaporated  the  colour  was  dark  cherry. 

Further  experiments  showed  the  following  results  :  If  a  per- 
fectly clean  tinned  iron  saucepan  is  used,  however  intense  the 
flame,  the  water  boils  in  the  usual  way,  and  the  tin  is  not  melted. 
The  surface  is  not  affected  by  the  heat  when  the  tinning  has 
been  removed  by  scraping  or  by  oxidation,  either  by  the  action 
of  humid  air  or  by  that  of  ammonia  or  hydrochloric  acid.  In 
either  state  of  the  surface  a  thin  layer  of  (oleonaphie]  mineral  oil, 
applied  cold,  does  not  interfere  with  regular  ebullition.  But  if 
the  oil  is  previously  decomposed  by  heat,  or  if  an  oily  rag  is 
laid  on  the  bottom  of  the  saucepan  and  held  there  by  a  weight, 
over-heating  immediately  takes  place.  The  same  effect  is  pro- 
duced if  a  solution  of  salt  is  evaporated  in  an  oxidised  saucepan, 
and  the  bottom,  when  covered  with  a  thin  crust  of  salt,  is 
smeared  with  cold  mineral  oil.  The  smallest  quantity  of  linseed 
oil  at  the  bottom  of  the  saucepan  immediately  produced  over- 
heating even  with  the  low  rate  of  evaporation  of  20  to  24  Ibs. 
Spirits  of  turpentine  and  oil  of  turpentine  did  not  produce 


THE  MODERN  STEAM  BOILER.  161 

overheating,  unless  mixed  with  a  small  quantity  of  linseed  oil. 
A  mastic  of  red  lead  easily  produced  overheating,  but  not  so 
quickly  with  colza  oil  as  with  linseed  oil.  Valvoline,  when  laid 
on  cold,  only  caused  a  dangerous  glow  when  the  heat  was  very 
intense — equivalent  to  a  yo-lbs.  evaporation. 

Pitch  at  the  bottom  of  the  tinned  saucepan  floated  off  when 
the  water  boiled  ;  it  adhered  to  an  oxidised  surface,  but  did  not 
cause  the  iron  to  become  unduly  heated. 

Limiting  Circumstances  to  the  Value  of  Experiments. — These 
investigations  are  undoubtedly  unique,  both  in  design  and  in 
importance  as  regards  our  subject,  and  they  were  the  fore- 
runners of  similar  inquiries  by  Durston,  Blechynden,  and 
Bryant.  There  are,  however,  some  circumstances  which  limit 
their  value  as  applied  to  the  larger  question  of  boiler  operation. 

1.  A  flat,  horizontal  surface,  such   as  that  of  the  plate  experi- 
mented with,  is  the  worst  for  freedom  of  supply  of  water  by 
circulation  when  boiling,  and  consequently  this  must  limit  the 
amount  of  heat  which  can  be  transmitted  through  it.     This  acts 
in  two  ways.     The  total  evaporation   in  a  given  time  per  unit  of 
surface  is  lessened,  and  the  degree  of  heating  the  plate  is  increased. 
A  dish-shaped  plate,  formed  like  the  contour  of  the  section   of 
the  furnace,  would  have  been  better  for  the  water  circulation  ; 
but  even  in  that  case  the  movement  of  the  water  could  not  have 
been  as  rapid  as  the   escape  of  the  steam  formed,  in  conse- 
quence of  the   difference  in  density  and  viscosity  of  the  two 
fluids. 

2.  The  plate  used  in  M.   Hirsch's    experiments    extended   a 
considerable    distance   beyond   the  furnace,    and    consequently 
some  heat  was  conducted  to  the  outer  portion  and  dissipated  by 
contact  with  the  air.     From  these  causes  it  is  probable  that  the 
plate  in  the  region  of  the  furnace  attained  a  higher  temperature 
than    should    be    necessary  for  a  given   evaporative  rate,    and 
yet  that  all  the  heat  employed  was  not  usefully  applied. 

3.  The    use  of  fusible  plugs    as    indicators  of  temperatures, 
however,    renders    it    uncertain    whether     the     temperatures 
recorded  were  actually  reached  by  the  plate.     Apart  from  the 
cause   of   uncertainty   referred  to    in    Chapter   II.,    p.    35,   the 
junction  of  metals  of  diverse  conductivities,  both  thermal  and 
electrical,    introduces   another    doubtful   element,  and  it  seems 
certain,  from  the  later  researches  of  Miss  E.  M.  Bryant,  that  the 

G 


162 


THE  PRACTICAL  PHYSICS  OF 


actual    temperature   of  the  plate  is  always  less  than    the    one 

indicated  by  the  melting  plugs. 

Nevertheless,  the  experiments  give  proof  that  an  evaporation 

of  from  50  to  nearly  100 
Ibs.  of  water  per  hour 
per  square  foot  of  heating 
surface,  may  be  attained, 
without  serious  heating 
of  the  metal  of  boilers, 
when  these  are  properly 
constructed  and  the  sur- 
faces are  clean. 

Blechynden's  Experi- 
ments.— The  experiments 
carried  out  by  Mr.  Blech- 
ynden,  in  1893,  are  even 
more  unsatisfactory,  from 
the  point  of  view  of  the 
circulation  of  the  water 
and  gases,  than  those  of 
M.  Hirsch,  although  Mr. 
Blechynden  took  precau- 
tions against  loss  of  heat 
by  radiation,  which,  as 
we  have  seen,  M.  Hirsch 
to  a  large  extent  neg- 
lected. The  diameter  of 
Mr.  Blechynden's  dish, 
or  "  boiler,"  \vas  smaller 
than  that  ot  M.  Hirsch's, 
and  the  furnace  was  not 
so  well  arranged,  but  the 
full  diameter  of  the  plate 
was  embraced  by  the  fur- 
nace casing. 

Mr.   Blechynden's    ap- 
FIG.  79*  paratus    is   illustrated   in 

Figs.  79  and  80,  in  which 

A   is    the  boiler,   B   the  furnace,  C   and    D    are    openings   for 

measuring  temperatures,  and  E  and   F  openings  for  escape  of 


THE  MODERN  STEAM   BOILER. 


163 


the  hot  gases.  The  boiler  (A)  was  10  inches  in  diameter  and 
12  inches  high  outside,  and  was  constructed  of  tinned  iron  plate 
about  24  B.W.G.  in  thickness, 
with  a  jacket  i  inch  wide  (i) 
on  its  sides  and  top,  covered 
with  (2)  asbestos  felt  -375  inch 
thick.  Usually  air  was  em- 
ployed in  the  jacket,  but  steam 
could  be  admitted  by  the  inlet 
(6)  and  made  to  pass  through 
to  the  outlet  (7).  At  first  the 
boiler  was  covered  with  only 
asbestos  felt,  without  the  air 
space  or  jacket.  The  plate 
to  be  experimented  with  (3) 
formed  the  bottom  of  the 
boiler,  which  was  soldered  to 
it,  the  two  pipes  (4)  and  (5)  at 
the  top  providing  for  the  ad- 
mission of  water,  the  escape 
of  steam,  and  the  insertion 
of  mercury  thermometers  to 
register  the  temperature  of  the 
water.  The  furnace  was  a 
cylindrical  chamber  (9)  of  sheet 
iron,  lined  with  firebrick  (10), 
(i  i)  and  (12)  being  the  openings 
near  the  top  for  exit  of  the 
gases,  and  (13)  and  (14)  holes 
for  insertion  of  the  copper 
balls  or  blocks  forming  part  of 
a  Siemens'  pyrometer,  which 


was    used    for    measuring   the 

furnace     temperatures.        Five 

jets    (15)   of    ordinary   lighting 

gas,  with   an  air  blast  from  a 

smith's     fire     supplied    flame,  ,.u;  8o 

which   was   passed   through    a 

mass  of  asbestos  lumps  (16),  covered  with  a  layer  of  wire  gauze 

(17)    in    order    to    distribute   the   flame   evenly.     At    (13)   the 

G   2 


1 64  THE  PRACTICAL  PHYSICS  OF 

pyrometer  block  was  suspended  at  a  distance  of  one  quarter 
to  one  half  inch  from  the  surface  of  the  plate,  and  at  (14)  the 
block  was  about  two  inches  from  the  incandescent  mass  of 
asbestos. 

Mr.  Blechynden  admitted  to  some  extent  the  uncertainty  of 
the  record  of  temperatures  afforded  by  the  Siemens'  pyrometer, 
but  his  estimate  of  error  was  too  low.  Such  a  method  can 
afford  merely  a  rough  approximation  to  the  actual  temperature 
of  the  spot  where  the  copper  block  is  heated.1  The  arrange- 
ment of  exit  tubes  or  passages  (n)  and  (12)  for  the  escape  of  the 
hot  gases  was,  moreover,  such  that  there  could  be  no  proper 
current  of  these  hot  gases  in  contact  with  the  heating  surface, 
that  surface  itself  being  also  of  a  bad  form  and  in  a  bad  position  for 
a  good  result.  If  the  top  of  these  exit  tubes  had  been  level 
with  the  bottom  surface  of  the  plate  (3),  this  would  have  ensured 
a  constant  renewal  of  the  portions  of  gas  in  contact  with  the 
plate  surface,  and  would  have  prevented  the  formation  of  local 
eddies,  which  Mr.  Blechynden's  arrangement  favoured.  It 
follows  from  this  that  even  the  temperatures  registered  by  the 
apparatus  at  C  were  not  likely  to  have  been  the  temperatures  at 
the.  underside  of  the  plate.  Further,  as  to  the  possibility  of 
adequate  circulation  of  the  water,  it  is  evident  that  Mr.  Blech- 
ynden relied  entirely  upon  the  natural  movement  produced  by 
the  act  of  boiling  in  the  confined  space  of  the  vessel,  but,  of 
course,  that  movement  depended  on  the  rate  at  which  ebullition 
proceeded  in  this  special  vessel,  and  was,  further,  hindered  by 
the  limited  quantity  of  water,  which  \vas  all  above  the  portion 
of  the  vessel  being  heated.  Under  the  circumstances,  there 
could  not  have  been  realised  as  good  a  result  as  would  have 
been  reached  with  additional  movement  of  the  water  and  gases 
over  the  surfaces  of  the  plate.  Apart  from  these  defects,  which 
were  inherent  to  the  process  employed,  the  experiments  were 
most  carefully  carried  out  and  considered.  First  of  all,  the 
temperatures  were  tested  by  removing  the  boiler  and  covering 
the  opening  with  asbestos  sheet  and  an  iron  plate.  Under 
such  conditions  the  temperature  reading  obtained  at  C,  D, 
E,  and  F  was  the  same,  viz.,  1780°  F.  The  boiler  was  then 

1  See  "  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland,"  Vol.  XXXVM 
pp.  143,  144. 


I! 


ia  si 


111 


-PLATE    // DIAGRflM   I 

I I87S "  THICK 


200  300  tOO  SOO  600  100  BOO  90O  1000  "MOO  1200  1300 

SCALE    OF  DIFFERENCE    Of    TEMPERATURES 


PLftTE  ft-    —DIRGRflM   III- 


100  tOO  300  900  MW  600  100  600  900  1OOO  1100  1200  i300 

SCfiLE    OF  DIFFERENCE   OF  TEMPERATURES 


k 
ll 


PLATE    /7 DIHGRHM  V 


II 


10  100 


ZOO  300  400  SOO  900  100  BOO  900 

SCALE    OF  DIFFERENCE  OF  TEMPERATURES 


—  PLflTL    A DIHGPHM  II 

75    THICK 


300  tOO  iOO  tOO  TOO  80Q  900  1OOO  11OO  lioO  1)00 

SCALE  OF  DIFFERENCE  OF  TEMPERATURES 


1 

l! 
!; 

i! 


PL/I  T£  A  DIAGRAM  IV- 


SCALE   OF  OlFflRlHCE   OF  UMPER/ITUR£S 


THE  MODERN  STEAM  BOILER.  165 

replaced,    and    the    temperature    readings   were    obtained    as 
follows  :— 

At  E,  F,  and  C         1545°  F. 

At  D 1850°  F. 

At  a  point  3^  ins.  under  the  plate 1580°  F. 

Mr.  Blechynden  very  properly  remarks  on  these  facts  :  "  It 
will  be  evident,  from  the  latter  experiment,  that  a  comparison 
of  the  evaporative  results,  or  the  quantity  of  heat  transmitted 
with  the  temperatures  measured  at  C,  would  be  misleading, 
and  would  incorrectly  represent  the  modulus  of  transmission, 
unless  the  quantity  of  heated  gas  passing  over  the  surface  of  the 
plate  were  unlimited  ;  the  comparison  should  be  with  some 
function  of  the  initial  and  terminal  temperatures.  But,  as  in  a 
considerable  number  of  the  earlier  experiments  the  tempera- 
tures at  C  only  were  measured,  a  comparison  of  the  evaporative 
results  will  be  made  with  these  temperatures,  from  which  it  will 
be  seen  that  such  broad  general  results  will  be  obtained  that, 
with  a  simple  correction  for  the  fact  of  the  temperatures  being 
terminal,  the  true  coefficient  of  transmission  may  be  fairly 
approximated."  It  is  thus  apparent  that  Mr.  Blechynden  had 
no  idea  of  attaching  to  these  experiments  anything  like  the 
final  or  absolute  value  which  many  have  invested  them  with 
since  their  publication,  and  therefore  that  any  relation  found  to 
exist  between  the  temperatures  observed  and  the  quantity  of 
heat  transmitted,  does  not  necessarily  hold  good  for  any  other 
conditions  than  those  under  which  these  observations  were 
made,  or  for  any  other  form  or  arrangement  of  apparatus. 

The  results  of  the  experiments  are  given  in  the  following 
Tables,  XXXII.  to  XXXIX.,  and  are  also  shown  graphically  in 
the  diagrams,  Figs.  81  and  82,  giving  the  general  results  for  all 
the  plates  shown  relatively  to  each  other  : — 


1 66 


THE  PRACTICAL  PHYSICS  OF 


TABLE  XXXII. 

RESULTS  OF  EXPERIMENTS  ON  THE  TRANSMISSION  OF  HEAT  THROUGH 

STEEL  PLATES. 
No.  i.  PLATE  A.  (SIDE  NEXT  WATER  MACHINED). 


Heat 

Duration 
of  Trial. 

Tempera- 
ture in 
Furnace 
at  C. 

Total 
Lbs.  of 
Water 
Evapor- 
ated. 

Heat  Units 
Transmitted 
per  Hour  by 
Heating  and 
Evaporation 
of  Water. 

Heat 

Units 
lost  by 
Radiation 
per  Hour. 

Total  Units 
(with  Radia- 
tion) Trans- 
mitted per 
Hour  per 
Sq.  Ft.  H. 

Difference 
in 
Tempera- 
ture D. 

Units 
Trans- 
mitted pei 
i  deg.  Diff. 
per  Sq.  Ft. 
per  Hour 
H 

H 
TT. 

Thickness 
of  Plate. 

Hrs.  Mins. 
I        51 

Deg. 
1  ,060 

10-15 

5,300 

600 

IO,820 

848 

1278 

•01505 

1-1875 

I       49 

1,205 

I4-0 

7,460 

„ 

14,780 

993 

i4'85 

•01498 

„ 

i       27 

1,225 

8-n 

7,845 

„ 

15,500 

1,013 

15-26 

•01505 

„ 

2        3 

1,425 

25-1 

11,800 

22,750 

1,213 

18-73 

•01545 

„ 

i      54 

1,440 

25-1 

12,750 

„ 

24,450 

1,228 

19-9 

•01622 

„ 

2      37 

1,490 

38-05 

1  3.950 

„ 

26,750 

1,278 

20-9 

•01637 

„ 

Mean 

•01552 

No.  2.     PLATE  A. 

i      4 

838 

3-44 

3,120 

600 

6,820 

626 

10-89 

•01741 

'75 

2         I 

I,OOO 

11-27 

5,380 

„ 

10,950 

788 

13-9 

•01765 

„ 

2          l£ 

1,125 

I5-45 

7,380 

„ 

14,650 

913 

16-04 

•01757 

,, 

i      33 

1,270 

16-79 

10,480 

„ 

20,300 

1,058 

19-18 

•01811 

i      48 

i,445 

.  26-45 

14-150 

„ 

27,IOO 

1,233 

21-92 

•01788 

„ 

Mean 

•01770 

No.  3.     PLATE  A. 

2        6 

775 

6-65 

3,058 

600 

6,7O5 

563 

11-90 

•02  1  10 

•5625 

i      57 

920 

9'97 

4,950 

„ 

10,  1  80 

708 

i4'37 

•O203O 

„ 

i      8} 

1,175 

11-85 

10,000 

,, 

19,450 

963 

20-18 

•02094 

„ 

i      7 

1,360 

17-98 

15,500 

,, 

29,550 

1,148 

25-7 

•02241 

., 

Mean 

•O2I19 

TABLE  XXXIII. 

No.  4.  PLATE  A.  (SIDE  NEXT  WATER  MACHINED).     • 

Heat 

Duration 
of  Trial. 

Tempera- 
ture in 
Furnace 
atC. 

Total 
Lbs.  of 
Water 
Evapor- 
ated. 

Heat  Units 
Transmitted 
per  Hour  by 
Heating  and 
Evaporation 
of  Water. 

Heat 

Units 
Lost  by 
Radiation 
per  Hour. 

Total  Units 
(with 
Radiation) 
Transmitted 
per  Hour 
PerSq.F, 

Difference 

Tempera- 
ture D. 

Units 
Trans- 
mitted per 
i  deg.  Diff. 
per.Sq.Ft. 
per  Hour 
H 

H. 

"Si 

Thickness 
of  Plate. 

D. 

Hr.  Mlns. 

Deg. 

I      51 

715 

5-06 

2,645 

600 

5,950 

503 

II'Sl 

•02350 

•25 

I      25 

858 

6-52 

4-450 

„ 

9,200 

646 

1435 

0-2230 

„ 

I      19 

935 

8-II 

5,930 

„ 

11,970 

723 

I6-55 

0-2290 

,, 

I      I4 

1,040 

9'97 

7,820 

„ 

15,450 

828 

18-65 

0-2255 

„ 

i      7 

1,105 

10-9 

9,460 

H 

I8,470 

893 

20-65 

0-2310 

„ 

i      7 

1,190 

13-61 

11,750 

„ 

22,650 

97 

23-I5 

0-2365 

Mean 

•02300 

PLATE   B—  DIAGRAM  VI 


zoo  goo  foo  goo  goo  -too  goo  9oo          tooo         1100          lioo         -idoo 

SCALE  Of  DIFFERENCE   OF   TEMPERATURES 


ffl 


PLATE  B-  DIAGRAM  VIII 


4VO  5VO  ffOO  TOO  gOO  90O  1OOO 

SCALE   OF  DIFFERENCE    OF    TEMPERATURES 


13OO 


i 

' 


r 

3i 


DIAGRAM    X  — 

POINTS  JOJR_PLATE_    fl_ MARKED  THUS       Q_ 


SCALE   OF   THICKNESS. 


•—  PLATE:  B- DIAGRAM  VII- 

31 5' THICK. 


100  ?no  300  tOO  500  600  700  800  POO 

SCALE  Of  DIFFERENCE  OF  TEMPERATURES 


IB* 


5 


MOO  itOO  t300 


lill 


too  300  Voo  fno  aoo  too  ebo  <foc         1000          1100 

SCALE   OF  DIFFLBZNCt.  .OF    TEMPERATURES 


THE  MODERN  STEAM  BOILER. 


167 


TABLE    XXXIII.   (continued). 
NO.  5.     PLATE  A. 


Heat 

Total  Units 

Units 

Duration 
of  Trial. 

Tempera- 
ture in 

Furnace 

at  C. 

Total 
Lbs.  of 
Water 
Evapor- 
ated. 

Heats  Units 
Transmitted 
per  Hour  by 
Heating  and 
Evaporation 
ot  Water. 

Heat 
Units 
lost  by 
Radiation 
per  Hour. 

(with 
Radiation) 
Transmitted 
per  Hour 
per  Sq.  Ft. 

Difference 
in 
Tempera- 
ture D. 

Trans- 
mitted per 
i  deg.  Diff. 
per  Sq.  Ft. 
per  Hour. 

H. 
.D~a. 

Thickness 
of  Plate 

IX 

Hr.  Mins. 

I        3 

950 

6-55 

6,030 

600 

12,170 

738 

16-48 

•02230 

•125 

I         I 

1,  1  2O 

10-18 

9,690 

„ 

]<S,<  SO 

908 

20-75 

•02285 

„ 

I      25 

1,210 

18-27 

12,500 

24,030 

998 

24-1 

•02415 

„ 

i      6 

1,295 

16-48 

14,460 

„ 

27,620 

1,083 

25-48 

•02352 

„ 

I     24 

1,335 

23-28 

l6,IOO 

30,620 

1,123 

27-25 

•02426 

„ 

i     13 

1,345 

20-45 

16,240 

„ 

30,900 

1,133 

27-27 

•02410 

„ 

l     13 

i,35o 

20-65 

16,450 

„ 

31,300 

1,138 

27-48 

•02410 

„ 

i       3 

i,530 

26-IO 

24,000 

,, 

45,100 

I,3l8 

34-21 

•02595 

,, 

Mean 

•02390 

TABLE  XXXIV 
No.  6.     PLATE   B.     (SIDE  NEXT  WATER  MACHINED). 


Duration 
o»  Trial. 

Tempera- 
ture in 
Furnace 
at  C. 

Total         Heat  Units 
I  bs  'of      Transmitted 
W  iter      Per  Hour  bv 
Evajor-    Heatintf  and 
ated         Evaporation 
of  Water. 

Heat 

Units 
lost  by 
Radiation 
per  Hour. 

Total  Units 
(with 
Radiation) 
Transmitted 
per  Hour 
per  Sq.  Ft. 
H. 

Difference 
in 
Tempera- 
ture D. 

Heat 

Units 
Trans- 
mitted per 
i  deg.  Diff. 
perSq   Ft. 
per  Hour. 
H 

H. 

D^. 

Thickness 
of  Plate. 

209 

000 

TT 
10-32 

•02495 

•46875 

Hr.  Mins. 
I      1O 

DeK'. 
625 

i,73o 

4,270 

413 

I        7 

850 

5-09. 

4,400 

„ 

9,175 

638 

14-38 

•02255 

„ 

I      23 

855 

6-41 

4-500 

,, 

9,350 

643 

i4'53 

•02260 

„ 

I         O 

1.205 

12-68 

12,235 

23,550 

993 

2370 

•02385 

,, 

I      30 

1,240 

20-64 

13,300 

„ 

25,500 

1,028 

24-80 

•02410 

„ 

i.      8 

1,280 

17-23 

14,720 

•    ., 

28,140 

1,068 

26-30 

"02462 

„ 

i     19 

i,335 

21-86 

16,000 

30,450 

1,123 

27-10 

•O24IO 

,, 

I         0 

1,340 

16-82 

16,230 

„ 

30,850 

1,128 

2734 

•02425 

„ 

i      3 

1,360 

1828 

16,800 

„ 

31,940 

1,148 

27-80 

•02420 

„ 

I         O 

1,465 

21-38 

20,610 

38,950 

1,253 

31-10 
Mean 

•02474 

" 

•023996 

No.  7.     PLATE  B. 

i       3 

862 

5'0 

4,6io 

600 

9,570 

650 

I4-74 

•O2270 

•375 

I       10 

868 

6-15 

5,080 

„ 

10,420 

656 

I5'87 

•02421 

„ 

i     17 

1,170 

15-69 

11,800 

„ 

22,750 

958 

23-74 

•02479 

„ 

i      8 

1,180 

13-92 

11,880 

„ 

22,880 

968 

23-62 

•02440 

„ 

I      4 

1,320 

17-62 

16,000 

„ 

30,400 

1,108 

27-40 

•02472 

„ 

I      21 

i,5oo 

30-7 

22,000 

„ 

41,450 

1,288 

32-15 

•02498 

n 

i      8i 

1,520 

27-0 

22,9IO 

M 

43,150 

1,308 

33'0 

•O252O 

„ 

Mean 

•02443 

i68 


THE  PRACTICAL  PHYSICS  OF 


TABLE  XXXV. 
No.  8.     PLATE  B.     (SIDE  NEXT  WATER  MACHINED). 


Duration 
of  Trial. 

Hrs.  Mins. 
I       4 

Tempera- 
ture in 
Furnace 
atC. 

Total 
Lhs.  of 
Water 
Evapor- 
ated. 

Heat  Units 
Transmitted 
per  Hour  by 
Heatinj;  and 
Evaporation 
of  Water. 

Heat 
Units 

lost  hv 

Radiation 

per  Hour. 

Total  Units 
(with 
Radiation  1 
Transmitted 
per  Hour 
per  Sq.  Ft. 
H. 

3,595 

Difference 
in 
Tempera- 
ture 1). 

.373 

Heat 
Units 
Trans- 
mitted per 
i  cleg  Diff. 
per  Sq.  Ft. 
per  Hour. 
H. 

TT 

H. 

u^. 
•02584 

Thickness 
of  Plate. 

Deg. 

585 

I'S 

1,360 

600 

9-63 

•25 

I        I 

725 

3'13 

2,975 

„ 

6,560 

513 

12-77 

•02495 

„ 

I       10 

985 

8-93 

7,410 

„ 

14,700 

773 

19-0 

•02460 

,, 

i      9 

1,035 

10-45 

8,780 

„ 

17,220 

823 

20-94 

•02544 

,, 

o    57 

1,060 

9'25 

9,370 

„ 

18,310 

848 

21-6 

•02545 

„ 

i     15 

1,067 

12-66 

9,770 

„ 

19,020 

855 

22-28 

•02600 

„ 

i      4 

1,320 

18-15 

16,500 

„ 

3i,38o 

i,  108 

28-3 

•02550 

„ 

I       12 

i,340 

2  1  '62 

17,460 

„ 

33,i5o 

1,128 

29-39 

•02604 

„ 

I       6 

1,480 

26-55 

23,300 

" 

43,800 

1,268 

34'6 
Mean 

•02730 

" 

•02568 

No.  9.     PLATE  B. 

i     17 

755 

4-67 

3,520 

600 

7,550 

543 

13-88 

•02558 

T5625 

I       20 

950 

9-38 

6,780 

„ 

13,540 

738 

18-35 

•02490 

„ 

i      3 

1,185 

14-0 

12,850 

., 

24,650 

973 

25-3 

•02600 

„ 

i      7 

1,270 

I7-45 

15,150 

„ 

28,900 

1,058 

27-3 

•02583 

„ 

i      6 

i,335 

i9'65 

17,320 

„ 

32,900 

1,123  . 

29-28 

•02604 

„ 

I       10 

1,460 

27-8 

23,050 

, 

43,400 

1,248 

34'8 

•02790 

„ 

i      5 

i,475 

25-3 

22,550 

» 

42,400 

1,263 

33-58 

•02658 

WITH  AIR  JACKET.     NO  ADDITION  FOR  RADIATION. 

3     21 

At  C  &  D. 
588 

6-99 

2,019 

0 

3,7oo 

376 

9-86 

•02625 

air  jacket 

i     36 

717 

5-96 

3,595 

o 

6,600 

505 

13-06 

•02590 

„ 

2         0 

794 

10-28 

4,979 

o 

9,140 

582 

15-67 

•02690 

„ 

I       46 

i,34i 

32-6 

17,850 

o 

32,750 

1,129 

29-10 

•02570 

„ 

I      21 

i,367 

25'95 

18,540 

o 

34,050 

i,i55 

29-48 

•02550 

„ 

I      32 

1,450 

35'i 

22,100 

0 

40,550 

1,238 

32-78 
Mean 

•02650 

" 

•0261  1 

THE  MODERN  STEAM   BOILER. 


169 


TABLE  XXXVI. 

No.  9A.     PLATE  B.  (SIDE  NEXT  WATER  MACHINED). 
WITH  AIR  JACKET.     NO  ADDITION  FOR  RADIATION. 


Heat 

Units 

Heat 

Trans- 

Units 

Duration 
of  Trial. 

Temp,  at 
Top  of  i 
Furnace. 

Temp,  at 
Bottom  of 
Furnace. 

mitted  per 
Hour  by 
Heating 

Trans- 
mitted per 
Hour  per 

D 
Diff.Top. 

d 

Diff.   Bott. 

H 
D. 

H 
DXd. 

H 
DS. 

Thick- 
ness of 
Plate. 

and  Evap- 

Sq. Ft. 

oration  of 

H. 

Water. 

Hrs.  Mins. 

Deg. 

I        36 

717 

867 

3,595 

6,600 

505 

655 

I3'O6 

•01995 

•0259 

•0156 

2        0 

794 

904 

4.979 

9,140 

582 

692 

I5-67 

•02265 

•0269 

„ 

I         46 

1,341 

1,537 

17,850 

32,750 

1,129 

1,325 

29'IO 

•02195 

•0257 

„ 

I          21 

1,367 

1,850 

18,540 

34,050 

1,155 

1,638 

29-48 

•OlSoo 

•0255 

„ 

Mean 

•02064 

TABLE  XXXVII. 
No.  10.     PLATE  C.  (BOTH  SIDES  ROUGH). 


Heat 

Total  Units 

Units 

Duration 
of  Trial. 

Tempera- 
ture in 
Furnace. 

Total 
Lbs.  of 
Water 
Evapor- 
ated. 

Heat  Units 
Transmitted 
per  Hour  by 
Heating  and 
Evaporation 
of  Water. 

Heat 
Units 
lost  by 
Radiation 
per  Hour. 

(with 
Radiation) 
Transmitted 
per  Hour 
per  Sq.  Ft. 
H. 

Difference 
in 
Tempera- 
ture D. 

Trans- 
mitted per 
i  deg.  Diff. 
per  Sq.  Ft. 
per  Hour 
H 

H 

TV 

Thickness 
of  Plate. 

D. 

Hrs.  Mins. 
I      3 

•J5 

3  '95 

3,638 

600 

7,776 

652 

Il-gi 

•01829 

"8125 

I         2 

975 

570 

5,325 

„ 

10,860 

763 

I4-25 

•01865 

„ 

I         I 

985 

5'93 

5,630 

„ 

11,420 

773 

14-80 

•OI9I2 

„ 

r      9 

990 

6-07 

S.ioo 

„ 

10,450 

778 

I3-46 

•01730 

„ 

1      4 

990 

6-05 

5,475 

„ 

11,140 

778 

14-31 

•01841 

,, 

i      5 

1,060 

6'95 

6,200 

» 

12,475 

848 

1470 

•01735 

,, 

Mean 

•01819 

TABLE  XXXVIII. 
NO.  n.     PLATE  D.     (SIDE  NEXT  WATER  MACHINED). 


Heat 

Units 

Heat 

Duration 
of  Trial. 

Temp,  at 
Top  of 
Furnace 
atC. 

Temp,  at 
Bottom  of 
Furnace 
at  D. 

Trans- 
mitted per 
Hour  by 
Heating 
and  Evap- 

Units 
Trans- 
mitted per 

HS°UrFPter 

D 
Diff.  Top. 

d 
Diff.  Bott. 

H 

IT 

DXd. 

H 

D2. 

Thick- 
ness of 
Plate. 

oration  of 

H. 

Water. 

Hrs.  Mins. 

Deg. 

Deg. 

I        30 

651 

743 

2,318 

4-250 

439 

531 

9-66 

•OI82O 

'O22OO 

'5 

I        30 

967 

1,279 

7,180 

13,200 

755 

1,067 

17-49 

•01640 

•02316 

„ 

I        31 

950 

1.354 

7J40 

13,110 

738 

1,142 

17-75 

•01560 

•02428 

,, 

I        29 

956 

i,i77 

7,400 

13,580 

744 

965 

18-23 

•01892 

•02455 

„ 

2        40 

980 

1,280 

7,620 

13,980 

768 

1,068 

18-26 

•01710 

•02380 

„ 

I        4I 

1,059 

1,396 

8,820 

16,200 

847 

1,184 

19-13 

•01615 

•O226O 

„ 

I        40 

1,091 

1,347 

10,200 

18,730 

879 

1,135 

21-32 

•Ol88o 

0-2430 

„ 

I        33 

1,122 

1,422 

II.I2O 

20,410 

910 

1,210 

22-45 

•01858 

0-0247 

,, 

Mean 

•01747 

•02367 

THE  PRACTICAL  PHYSICS  OF 


TABLE  XXXIX. 
No.  12.  PLATE  E.  (MACHINED  ON  BOTH  SIDES). 


Heat  Units 

Heat  Units 

Duration 
of  Trial. 

Temp. 
Top 
at  C. 

Temp. 
Bott. 
at  D. 

Transmitted 
per  Hour  by 
Heating  and 
Evaporation 
of  Water. 

Transmitted 
per  Hour 
per  Sq.  Ft. 
H. 

D 
Diff.   Top 

d 
Diff.  Bott. 

H 
DX<*- 

H 

Thickness 
of  Plate. 

Hrs.  Mins. 

Deg. 

Deg. 

I      38 

513 

735 

774 

1,420 

301 

523 

•00901 

•01560 

1-1875 

i     53 

652 

896 

1,520 

2,790 

440 

684 

•00927 

•01442 

2      0 

856 

1,125 

2,855 

5,230 

644 

913 

•00890 

•01264 

2      2 

1,285 

i,55o 

8,800 

16,150 

1,073 

1,338 

•01126 

•01405 

„ 

Mean 

•00961 

•01418 

No.  13.     PLATE  E.     (MACHINED  ON  BOTH  SIDES). 

I       32| 

534 

648 

1,091 

2,005 

322 

436 

•01430 

•01938 

•1875 

2      O 

771 

989 

3,276 

6,010 

559 

Til 

•01382 

•01920 

„ 

2      0 

955 

1,242 

5/MI 

10,360 

743 

1,030 

'OI354 

•01880 

1    45 

i,34° 

1,625 

13,550 

24,880 

1,128 

i,4i3 

•01559 

•01955 

0 

Mean 

•01431 

•01923 

Boiler  surrounded  top  and  sides  by  air  jacket,  which  was  well  covered  with  asbestos. 
No  allowance  has  been  made  for  loss  b)-  radiation. 
This  plate  was  machined  on  both  sides. 

In  discussing  his  results  Mr.  Blechynden  said,  that  "if  an 
examination  be  made  of  the  Diagrams  or  Tables,  the  broad 
general  fact  is  evident  that  the  heat  transmitted  through  any  of 
the  plates  per  degree  difference  between  the  fire  and  the  water 
is  proportional  to  the  square  of  the  difference  between  the 
temperatures  at  the  two  sides  of  the  plate,  as  will  be  seen  from 
the  fact  that  the  ratio 

Heat  transmitted  per  square  foot. 
(Difference  of  Temperatures)  2 

is  a  constant  for  each  plate  within  the  limits  of  the  experiments, 
and  the  mean  values  of  this  ratio  for  the  various  plates  are 
given  in  the  table. 

"  The  figures  for -the  moduli  in  the  last  column  are  calculated 
as  for  the  mean  of  the  squares,  of  the  differences  of  the  tempera- 
tures on  the  assumption  that  the  temperatures  taken  just  over 
the  fire,  or  point  D,  are  the  maxima,  which  would  be  approxi- 
mately true,  and  that  those  at  the  upper  station  were  equal  to 
those  of  the  escaping  gases,  which  was  actually  correct.  The  mean 
of  the  squares  of  the  differences  of  temperatures  was  taken 


THE  MODERN  STEAM  BOILER. 


171 


TABLE  XL. 


Plates. 

Thickness. 
Inches. 

Modulus  for  Tempera- 
ture at  Top  Station. 

Modulus  for  Tempera- 
ture at  both  Upper 
and  Lower  Stations. 

A 

I-I875 

0-OI552 

A 

750 

•01770 

A 

•5625 

•02II9 

A 

•25 

•0230 

A 

•125 

•02390 

B 

•46875 

•023996 

B 

•3750 

•02443 

B 

•250 

•02568 

B 

•15625 

•O26ll 

•02064 

C 

'    8125 

•01819 

D 

•5OOO 

•02367 

•01747 

E 

I-I875 

•014178 

•00961 

E 

•1875 

•019235 

•OI43I 

as  being  D  </,  where  D  is  the  difference  between  the  tempera- 
ture at  the  upper  station  and  the  boiler,  and  d  the  difference 
between  that  at  the  lower  station  and  that  in  the  boiler. 

"  The  Table  shows  that  there  is  a  general  rise  in  the  value  of 
the  moduli  with  decrease  of  thickness  ;   but  if  the  diagram  Fig. 


POJJtTS  ^OR£LAT£_     A       MAKkCp  THUS        B_ 

B B „, Q 

0          if_  jg^ 


SCALC.    OF    THICKNfSS'- 

FIG.  82A. 


cSjA,  which  shows  graphically  the  general  relation  of  these 
moduli,  be  inspected,  it  will  be  seen  that  there  are  considerable 
irregularities  in  the  curves  joining  the  various  points  for  each 
plate.  This  is  perhaps  no  more  than  might  be  expected, 
because  of  the  great  difficulty  of  machining  all  the  surfaces  to 
the  same  degree  of  smoothness,  and  notwithstanding  the  pre- 
cautions taken,  the  difficulty  of  maintaining  the  surfaces  uniformly 


172  THE  PRACTICAL  PHYSICS  OF 

clean.  It  was  found  that  the  very  slightest  trace  of  grease 
caused  a  very  large  fall  in  the  rate  of  transmission  ;  even  wiping 
the  outer  surface  of  the  plate  with  a  piece  of  rag  or  of  waste 
was  sufficient  to  influence  the  result  detrimentally. 

"  There  is  also  an  apparent  falling  off  in  the  increased  effici- 
ency of  thinner  plates  when  they  are  under  three-eighths  of  an 
inch  or  so,  which  seemed  as  if  it  might  possibly  be  accounted 
for  on  the  assumption  that  the  thinner  plates  yielded  to  the 
cutting  tool,  and  thus  came  to  have  more  smoothly  machined 
surfaces  than  the  thicker.  That  the  smoothness  of  the  plates 
was  an  important  factor  wrill  be  readily  seen  when  the  position 
of  the  points  for  plate  E  are  compared  with  the  others." 

"  The  results  of  these  experiments/'  Mr.  Blechynden  finally 
remarked,  "  certainly  point  to  the  conclusion  that  the  thinner  the 
plates  forming  part  of  the  heating  surface  of  a  boiler,  the  higher 
should  be  the  boiler's  efficiency,  always  provided  that  the 
plates  are  clean  ;  but  it  will  be  evident  that  if  the  plates  be 
coated  with  a  covering  of  scale,  or  some  bad  conductor, 
then  the  less  must  be  the  influence  of  the  thickness  on  the 
efficiency,  while  with  a  thick  coat  of  oil  the  influence  might 
become  practically  unimportant.  The  fact  that  the  heat  trans- 
mitted is  proportional  to  the  square  of  the  difference  of  the 
temperatures  of  the  two  sides  of  the  plate,  shows  the  importance 
of  high  furnace  temperatures  if  efficiency  is  aimed  at,  and 
emphasises  the  importance  of  rapid  combustion  either  by  means 
of  air  supplied  by  fans  or  by  height  of  funnel." 

We  may  accept  these  conclusions  without  endorsing  all  the 
statements  connected  with  them.  It  is,  for  instance,  evident' 
that  the  temperatures  of  the  hot  gases  and  of  the  water — 
what  may  be  termed  the  temperatures  at  the  two  sides  of  the 
plate — are  confounded  with  the  temperatures  of  the  two  surfaces 
of  the  plate  itself.  In  consequence  of  the  very  minute  degree 
of  resistance  in  iron  plates  to  the  conduction  of  heat  through 
the  substance  of  the  metal,  it  is  not  likely  that  there  can  be  any 
considerable  difference  of  temperature  between  the  two  surfaces, 
even  while  a  large  amount  of  heat  may  be  passing  per  unit  of 
time  per  unit  of  surface.  For  the  transmission  of  a  large  amount 
of  heat,  there  must  no  doubt  be  a  large  difference  between  the 
temperature  of  the  hot  gases  and  that  of  the  water.  The  two 
sets  of  differences  are  therefore  far  from  being  identical.  The 


THE  MODERN  STEAM  BOILER.  173 

conditions  which  interpose  resistances  to  the  How  or  passage  of 
heat  from  the  gases  to  the  water  have  still  to  be  investigated. 

Reichsanstalt  Experiments. — Similar  experiments  to  those  of  Mr. 
Blechynden  were  carried  out  at  the  Reichsanstalt,  Charlotten- 
burg,  by  Dr.  Wiebe  and  Mr.  R.  Schwirhus,  between  1895  and 
1896,  and  are  recorded  in  the  Report  of  Professor  Kohlrausch, 
the  President  of  the  Institution.  A  comprehensive  authorised 
abstract  of^the  report  appeared  in  the  July  and  August  (1896) 
numbers  of  theZeitschrift  filr  Instniuiciiteiikunde ;  the  experiments 
on  tranmission  of  heat  through  metallic  plates,  being  at  pages 
235  to  240,  and  a  short  account  in  English  of  these  experiments 
was  given  in  Engineering,  Vol.  Ixiii.,  p.  31  (ist  January,  1897). 

Eleven  plates  were  used  in  these  experiments,  of  which  six 
were  steel,  three  were  wrought  iron,  and  two  were  copper.  All 
were  25  centimetres  (9*84  ins.)  in  diameter  and  the  original 
thickness,  of  either  1*2  in.  or  075  in.,  was  gradually  reduced 
down  to  0'2  in.  in  some  instances.  The  furnace  and  boiler 
arrangements  resembled  those  of  Blechynden,  except  that  disc 
grates  were  inserted  to  effect  a  thorough  mixing  of  the  gases 
and  a  uniform  temperature  over  the  surface  of  the  fire,  and 
Le  Chatelier  thermo-couples  were  employed  to  measure  the 
temperature  at  4  centimetres  or  i-6  in.  below  the  plate  under 
test. 

Seventy-eight  experiments  were  made  with  the  steel  plates,  35 
with  the  wrought  iron,  and  12  with  the  copper  plates. 

Originally,  both  surfaces  of  the  plate  were  in  the  state  left  by 
the  mill  or  foundry,  and  the  reduction  of  thickness  was  effected 
by  turning  down  the  inner  surface  which  was  exposed  to  the 
water,  the  outer  surface,  exposed  to  the  gases,  t  remaining  rough. 
Some  tests  with  plates  polished  on  both  surfaces  were  also  made, 
and  one  or  two  with  artificial  incrustations  on  the  water  surface. 
These  imitation  incrustations  were  composed  of  cement  and  sand, 
or  of  actual  boiler  crust  powdered  and  mixed  with  oil,  and  their 
thickness  was  varied  between  0*2  and  0*3  in. 

The  temperature  at  the  fire  side  of  the  plate  was  varied,  the 
quantity  of  water  evaporated  at  each  temperature  being  observed 
for  a  period  which  extended  to  from  i  to  2\  hours  in  different 
experiments. 

All  the  observations  were  recorded  in  a  series  of  diagrams,  in 
which  the  abscissas  are  degrees  Centigrade  and  the  ordinates  are 


J74 


THE  PRACTICAL  PHYSICS  OF 


kilogramme-calories  per  hour  per  degree.    The  diagonal  straight 
lines  were  simply  added  for  comparison  and  do  not  indicate  the 

position  of  the  results  other- 
wise. The  Roman  numerals 
at  the  ends  of  these  lines 
denote  the  various  plates, 
of  which  IV.,  V.,  and  VI. 
were  wrought  iron,  and  the 
others  in  Fig.  83  were  steel. 
The  numbers  2  and  3 
below  the  lines  are  placed 
to  indicate  the  point  of 
corresponding  value  on 
each  line,  because  the  dia- 
grams overlap  each  other. 

In  the  case  of  plate  I.  the 
mark  +  refers  to  the  ori- 
ginal plate,  •  to  the  plate 
covered  with  mud  or  scale, 
O  to  the  thickness  of  10*5 
millimetres,  ©  to  the  thick- 
ness 7-5  millimetres. 

In  II.,  thickness  of  287 
mm.  is  indicated  by  -f ,  19*0 
mm.  by  O,  and  of  12*2 
mm.  by  •  ;  in  III.,  +  = 
30-5,  and  O  =  30*5  mm., 
both  surfaces  crude  ;  in  IV., 


vi 


vn 


vm 


20*9  mm.,  with  upper  sur- 
face turned,  or  in  the  third 
instance  bright  ;  V.,  +  = 
2O'4  mm.  turned  ;  VI.,  +  = 
30^2  mm.  both  surfaces 
crude  ;  VII.,  +  =  15*6, 
O  =  ii'o  mm.  turned  at 
the  upper  surface  ;  VIII., 

+  =11*5  mm.  turned  at  the  upper  surface  ;  IX.,  +  =  18*2  mm. 

both  sides  crude. 

With  plate  No.  I.  at  a  thickness  of  30*5,  mm.  (1*2  in.),  heat  was 


+     =    29-0, 


=    21-2,     • 


600- 

FIG.  83. 


COO' 


700 


THE  MODERN  STEAM  BOILER. 


175 


transmitted  at  temperatures  /  =  374,  433,  468,  480,489,  561,  628, 
654,  674  degrees  C.,  at  the  rate  of  Q  (kilog.-cals.j  =      w  53      = 

2-16,  2-39,  275,  274,  3-01,  3-15,  3-35,  3-63,  4-01  kilogramme- 
calories  per  hour  per  degree.  The  plate  was  then  turned  down 
on  the  upper  surface  until  it  was  10-5  mm.  (0*41  in.)  thick,  and 
gave  at  temperatures  /  =  346,  406,  484,  603  ;  Q  =  174,  2*08, 
2'59,  3*24.  Again  turned  down  to  a  thickness  of  7^5  mm. 
(0-29  in.),  it  showed  at  /  =  308,  409,  503,  517,  573  ;  Q  =  1-51, 
2^14,  2^89,  2*63,  3*34.  Finally  reduced  to  a  thickness  of  5*4  mm. 
(o'2i  in.),  the  lower  surface  having  remained  unchanged  all  the 
time,  we  have  for  /  =  319,  418,  499,  606  ;  Q  =  i'54,  i'99,  2^58, 
3*63.  The  experimenters  do 
not  claim  an  accuracy  of  more 

than   ""  10  per  cent. 

The  two  copper  plates  ex- 
perimented with  had  thick- 
nesses of  +  =  29-5  mm. 
(n6in),  and  Q  =  3°  mm. 
(ri8  in.)  ;  the  former  was 
polished  on  the  upper  or 
inner  side,  the  under  side 
not  being  worked  in  any  way. 
The  results  are  shown  in  Fig. 
84,  the  straight  diagonal  line 
being  the  same  as  in  the  iron 
and  steel  tests  in  Fig.  83. 

In  these  experiments,  the  thickness  of  the  iron  and  steel  plates 
and  the  state  of  their  surfaces  seemed  to  have  scarcely  any 
influence  upon  the  heat  transmission.  The  fact  that  the  various 
points  of  the  curves  belonging  to  plates  of  different  thicknesses  lie 
close  together,  indicates  that  whatever  may  be  the  transmission 
resistances  acting  between  the  plate  and  the  media  on  both 
sides  of  it,  the  resistance  in  the  metal  is  insignificant  for  the 
thicknesses  experimented  with.  "  The  temperatures  /  of  the 
gases  below  the  plate  and  100°  C.,  that  of  the  boiling  water 
above  it,  must  widely  differ  from  those  of  the  surface  layers 
of  the  iron.  If  there  were  no  such  differences,  Q  should  be 
for  thicknesses  of  i,  2,  and  3  centimetres,  300,  150,  and  100 


FIG.   84. 


176  THE  PRACTICAL  PHYSICS  OF 

kilog.-cals.,  whilst  in  reality,  the  observed  values  of  Q  have 
varied  between  i,  3,  and  4  only  ;  that  is  to  say,  have  been  small 
fractions  of  the  calculated  values." 

Artificial  incrustations  did  not  seem  to  have  much  effect  be- 
yond increasing  the  time  required  to  raise  the  water  to  boiling 
point.  Afterwards,  the  amount  of  heat  transmitted  did  not  seem 
to  be  affected.  "  Plate  I.  was  also  tinned  above  ;  this  had 
apparently  an  injurious  effect.  In  order  further  to  ascertain 
whether  the  condition  of  the  lower  surface  exposed  to  the  gases 
would  have  any  influence,  Plates  II.,  now  12  mm.  (0*47  in.) 
and  V.,  20  mm.  (079  in.)  thick,  were  fairly  polished  on  both 
sides.  The  heat  transmitted  was  unmistakably  decreased. 
Between  the  temperatures  t  =  311  and  616,  Q  rose  from  1*59  to 
3*50,  when  the  lower  surface  had  not  been  touched  and  from 
i '26  to  2'o  when  that  surface  had  been  polished." 

Although  the  position  of  the  diagonal  lines  seems  to  corres- 
pond with  Rankine's  approximate  formula,  expressing  that  the 
heat  transmitted  is  proportional  to  the  square  of  the  difference 
of  temperature,  it  is  pointed  out  that  these  experiments  contain 
evidence  that  it  is  not  safe  to  generalise  from  that  empirical  rule. 
"  It  does  not  hold  for  plates  bright  below,  and  certainly  not  in 
the  least  for  copper  plates."  Copper  transmits  heat  at  the 
higher  temperatures  less  rapidly  than  iron.  On  the  other 
hand,  iron  and  steel  oxidise,  and  are  more  subject  to  gradual 
deterioration  from  this  cause  than  copper.  These  points, 
no  doubt,  influence  the  above-mentioned  transition-resistance, 
and  further  research  is  needed  to  investigate  that  portion  of  the 
subject. 

One  very  important  result  of  these  experiments  remains  to  be 
noticed,  as  it  illustrates  a  point  which  has  been  repeatedly 
pressed  in  these  pages,  viz.,  the  vital  effect  of  movement  of  the 
hot  gases.  By  altering  dampers,  etc.,  the  same  temperature  of 
400°  C.  was  produced  and  maintained  with  an  increased  velocity 
of  the  ascending  hot  gaseous  currents  at  each  fresh  experiment. 
In  three  tests  under  these  altered  conditions  the  evaporation 
was  at  the  rate  of  1*035,  ro86,  and  1-098  kilogrammes  of  water 
per  hour. 

These  experiments  were  subject  to  the  same  drawbacks  as 
were  those  of  Mr.  Blechynden  with  regard  to  the  application  of 
the  heat  to  the  plate  or  dish  containing  the  water,  and  the  later 


THE  MODERN  STEAM  BOILER. 


177 


investigations  of  Miss  E.  M.  .Bryant,  B.  Sc.,1  introduce  some  con- 
siderations based  on  the  state  of  the  surface  of  the  plates,  which 
also  modify  the  result. 

Bryant's  Experiments. — Miss  Bryant  followed  M.  Hirsch  in  the 
form  of  apparatus  employed,  but  introduced  •  some  important 
modifications,  the  use  of  fusible  plugs  being  abandoned  in  favour 
of  thermo-electric  junctions  embedded  in  the  substance  of  the 
plates  at  different  depths  below  the  water  surface,  and  in  the 
hemispherical  iron  cup  placed  in  the  furnace.  The  heating  was 
carried  out  by  radiation  from  the  inner  surface  of  this  metal  cup, 
the  gas  flames  from  two  Fletcher  oxygen  burners  playing  upon 
the  outside  of  it  within  the  fire-brick  casing  of  the  furnace.  The 
dish  containing  the  water, 
of  which  vessel  the  plate 
under  test  formed  the  bot- 
tom, was  shielded  against 
heating  in  any  way  but 
directly  through  the  plate 
by  means  of  a  guard-ring 
consisting  of  an  outer  an- 
nular vessel  B,  made  of 
sheet  copper  and  contain- 
ing water.  Figs.  85  and  86 
show  the  general  arrange- 
ment of  apparatus  —  the 
method  of  feeding  the 
water  was  the  same  as  in  M.  Hirsch's  experiments.  A  is 
the  inner  vessel  with  the  experimental  plate  for  its  bottom, 
the  outer  edge  of  the  plate  being  insulated  by  means  of  a 
lining  of  asbestos  or  similar  non-conductor  in  the  space 
between  A  and  B.  The  degree  of  heat  to  which  the  metal 
plates  experimented  with  were  exposed  was  necessarily  limited 
by  the  temperature  to  which  the  hemispherical  cup  was 
raised  ;  all  the  heat  having,  moreover,  to  reach  the  plates 
by  radiation,  as  there  could  be  no  circulation  of  hot  air  or 
gases,  except  that  of  the  very  limited  quantity  of  air  in  the 
hemispherical  space  enclosed.  The  Tables  of  results  disclose 
that  the  temperature  of  the  cup  varied  only  between  600°  and 


FIG.   85. 


1  Min.  Proc.  Inst.  C.E.,  Vol.  cxxxii.,  p.  274. 


i78 


THE  PRACTICAL  PHYSICS  OF 


942°  C.,  and  wras  most  frequently  maintained  at  from  700°  to 
850°  C.,  but  these  temperatures  are  considerably  lower  than 
those  to  which  the  iron  or  steel  of  boilers  is  exposed  in  actual 
work.  Moreover,  the  transmission  readings  were  not  taken 
until  the  temperatures  both  of  the  plate  and  of  the  hot.  wall  of 
the  metal  cup  remained  steady,  but  this  showed  only  that  the 
point  of  maximum  rate  of  transmission  for  this  apparatus,  as  it 
was  arranged,  had  been  reached.  The  velocity  of  the  circula- 
tion of  the  water  is  an 
important  element  in  the 
rate  of  transmission,  be- 
cause it  is  the  water 
which  carries  off  the  heat 
which  passes  through  the 
metal  plate.  Unfortu- 
nately, the  shape  and 
size  of  the  circular  vessel 
A  were  against  anything 
but  a  very  moderate 
speed  and  restricted  kind 
of  circulation,  and  con- 
sequently the  maximum 
rate  with  such  a  vessel 
would  not  necessarily 
be  the  maximum  rate  of 
transmission  with  other 
arrangements.  The  fact 
of  the  heating  being 
carried  out  almost  en- 
tirely by  radiation  also 

gives  a  very  limited  range  -of  value  to  these  experiments, 
because  such  conditions  are  entirely  artificial,  and  necessarily 
restrict  the  degree  of  heating.  The  paper  of  Miss  Bryant 
itself  contains  evidence  that  when  the  hot  gases  were  allowed 
to  strike  against  the  metal  plate  a  much  higher  rate  of  transmission 
was  reached.  One  Table  (XLV.)  records  a  series  of  experiments 
with  a  copper  plate,  in  which  the  gases  were  allowed  to 
strike  directly  on  the  plate,  and  the  numbers  of  C.G.S.  heat 
units  transmitted  per  minute,  which  in  the  former  experi- 
ments with  radiation  heating  ranged  from  3,820  to  8,540, 


SECTION    OF  BOILER    AND    FURNACE. 


FIG.   86. 


THE  MODERN  STEAM  BOILER. 


179 


200  ZAO 


320      330 


4-0  80  ISO  !••  200  ZAO  280 

HEAT    UNITS    TRANSMITTED    PEP.     SI?     CM.     PER     MINUTE 

CURVES  SHOWING  THE  TEMPERATURE  OP  THE  FIRE  SIDE  OF  THE  PLATE  AT 
DIFFERENT  RATES  OF  EVAPORATION 

FIG.  87. 


THICKNESS     OF     PLATE      IN      HUNDREDTHS      OF      AN     INCH 

O'KVKS  SHOWING  THK  INCREASE  OF  TEMPERATURE  OF  THE  PlKK  SlDK 

OF  THE   PLATE   WITH    INCREASE  OF  THICKNESS  AT  DIFFERENT  RATES 

OF  EVAPORATION. 

KIG.   88. 


180  THE  PRACTICAL  PHYSICS  OF 

at  once  rose  to  from  4,700  to  16,050.  Moreover,  the  paper 
contains  the  following  significant  remarks  :  "  While  the  boiler 
was  being  heated  before  an  experiment,  a  blast  of  air  was  sent 
into  the  hemispherical  space  below  the  plate.  This  prevented 
the  hot  gases  from  coming  in  contact' with,  and  condensing 
upon,  the  cold  iron,  and  thus  prevented  the  rusting.  This  blast 
was  stopped  before  the  measurements  were  taken,  as  if  left  on 
it  largely  increased  the  circulation  of  air,  and  the  result  was  an 
increase  of  evaporation  for  the  same  temperature  of  the  hot 
wall."  This  may,  of  course,  be  read  in  either  of  two  ways,  but 
in  view  of  the  results  given  in  Table  XLV.  we  might  be  justified 
in  taking  the  increased  evaporation  as  the  result  of  the  increased 
circulation  of  air  when  the  plate  was  hot.  There  is  no  manner 
of  doubt  that  if  movement  of  the  water  is  essential  to  rapidity 
of  heat  transmission,  movement  of  the  hot  gases  is  much  more 
necessary  and,  moreover,  a  much  more  rapid  movement  is 
essential  in  this  case.  On  this  branch  of  the  subject,  however, 
Miss  Bryant's  experiments  throw  no  further  light. 

The  twro  preceding  diagrams  (Figs.  87  and  88)  are  given  to 
show  that  in  these  experiments  the  temperature  of  the  fire 
surface  of  the  plate  (through  which  heat  is  being  transmitted 
to  the  water)  increases  directly  as  the  rate  of  flow  of  heat 
through  the  plate,  and  also  increases  with  the  thickness  of  the 
plate  when  the  rate  of  evaporation  is  constant.  The  water 
surface  of  the  plate  was  found  in  these  experiments  to  be 
between  3°  and  12°  C.  above  the  boiling  point  of  water.  The 
results  obtained  with  copper  and  steel  plates  are  given  in  the 
succeeding  Tables  XLI.  to  XLV. 


THE  MODERN  STEAM  BOILER. 


181 


TABLE  XLI.-COPPER  PLATE.     THICKNESS,  0904  INCH  =  23  CENTIMETRES. 
AREA,  96-3  SQUARE  CENTIMETRES. 


0 

K 
•o<-> 

ismitted 
:e. 

'aporated 
per  Hour. 

if 

|u 

I 

ill    L 

Date,  1895. 

li 

Ste 

1 

II 
1 

K 

Lbs.  ot  Water  Ev 
per  Square  Foot 

C.G.S.  Heat-Ui 
Square  Centim 
Minute. 

Temperature  of 
Surface  in 

Temperature  ol 
Surface  in 

Difference  of  T 

ture  between  U] 
Lower  Surfaces 

Duration  of  Exf 
in  Minutt 

Condition   of 
Surface. 

Nov.     7      I 

759-5 

4,220 

IO'O 

43'9 

102-6 

107-0 

4'4 

2O'O 

Oxide. 

„      7     U 

770-0 

4,680 

in 

48-6 

I02'6 

107-1 

4'5 

12-0 

,, 

„       12         I 

820-0 

5,170 

12-3 

53-7 

28-5 

„ 

„       12      U 

723-0 

4,090 

9-9 

42-5 

103-6 

loS'O 

4'4 

20'O 

„       13         I 

769-0 

6,970 

16-6 

723 

IO5-O 

1  1  1'6 

6-6 

I7-0 

f  Slightly  black- 
t      ened" 

„     13     II 

786-0 

7,240 

17-2 

,     75'2 

105-1      lira 

6-1 

I4-5 

]  Slightly  black- 
\     ened. 

„     IS     - 

627-0 

3,820 

9'8        397 

104-0       io6'8 

2-8 

24-0 

Smoked. 

,.     18       I 

746-0 

6,260 

14-9        65'o 

106-8       1  1  2-1 

5'3           30-5 

„ 

.,     18     II 

773-0 

6,800 

16-4       ,71-6 

106-7       112-5 

5'8          SI'S 

,, 

„     18  III 

787-0 

7,5io 

17-9        78-0 

106-8      112-7 

5'9          22-0 

„     19      I 

807-0 

7,990 

19-0        83-0 

107-2       113-2 

6-0          15-0    '          „ 

„     19     11 

825-0 

8,540 

20-3        88-6 

107-8       113-8 

6-0          15.0    i 

TABLE  XLII.— STEEL  PLATE.     THICKNESS  1015    INCH   =  2-58  CENTIMETRES. 
AREA.,  1054  SQUARE  CENTIMETRES. 


1 

ll 

ii 

II 

.2  S 

*„ 

1  1  IK 

1 

-50 

u>  C. 

>  o. 

-» 

**• 

K    Q,— 

i>ji 

Date,  1895. 

S  a 

ll 

1! 

III 

gjj 

s£ 

ll 

ifi 

w  g 

Condition  of 
.    Surface. 

H 

gi 

p 

31 

1! 

H 

U 

in 

Q 

Nov.  30     ... 

775-0 

8,780 

19-1 

83-4 

1O7-0 

139-8 

32-8 

26-0 

Dec.     2    II 

7OI-O 

6,280 

13-6 

59-6 

108-8 

137-6 

28-8 

29-0 

,.         2    III 

750-0 

7,180 

15-6 

68-1 

I09-0 

141-0 

32-0 

23-5 

„        2     IV 

773-0 

7,420 

16-5 

70-4 

109-6 

144-1 

34-5 

9-0 

Smoked    and    a 

„        2       V 

7780 

8,310 

18-1 

78-9 

I  lO'O 

145-3 

35-3 

I2'O 

'    little  rusted. 

4     ... 

796-0 

9,090 

19-8 

86-2 

107-9 

147-5 

39-6 

24-5 

„      5      1 

731-0 

7,060 

I5-4 

67-0 

105-4 

135-8 

30-4 

22-5 

„      5     II 

648-0 

4.815 

10-5 

45-6 

103-9 

125-8 

21-9 

I3-0 

„      7      I 

7II'0 

6,910 

15-0 

65-6 

108-0 

134-0 

26-0 

17-0 

)  Rusted  round  the 

„      7    U 

62I-Q 

4,380 

9'9 

4I-5 

107-0 

124-9 

17-9 

I2'5 

("edges  and  smoked. 

„       12         I 

834-0 

9,640 

21'0 

9I-5 

108-1 

143-2 

35'i 

18-0 

]  Somewhat   irre- 

„      12      U 

841-0 

9,820 

21-3 

93-2 

108-1 

144-8 

36-7 

22-5 

>•     gularly  rusted 

„      12    III 

748-0 

6,470 

I4-I 

61-4 

106-8 

133-4 

26-6 

13-0 

1      and  smoked. 

,,     13       I 

766-0 

7,450 

16-2 

70-7 

105-2 

135-0 

29-8 

33'0 

\  Rusted    chiefly 

„     13     II 

545-0 

2,920 

6'4 

27-8 

104-0 

1  16-8 

12-8 

21-0 

j      at  edges  and 
'      smoked. 

„     14     ... 

793'5 

5.460 

11-9 

5I-9 

106-5 

131-0 

24-5 

i6'o 

„     16      I 

807-0 

6,040 

13-1 

57-3 

105-5 

129-9 

24-4 

3i-o 

Rusted  slightly 

,,     16     11 

688-0 

3,930 

8-5 

37-3 

1043 

120-9 

1  6-6 

20-5 

all  over.     No 

„     17       I 

834-0 

7,380 

16-1         701 

104-7 

134-8 

30-i 

32-5 

smoke. 

„     17     U 

736-0 

4,710 

10-2            44-8 

105-3     124-7 

19-4 

2IX> 

. 

182 


THE  PRACTICAL  PHYSICS  OF 


TABLE  XLI1I.-STEEL  PLATE.     THICKNESS,  256  CENTIMETRES. 
AREA,  1054  SQUARE   CENTIMETRES. 


0 

X 

J 

P 

£ 

1 

1 

1  | 

1 
I 

•gci 

1* 

|JL 

"5  "£  . 

0 

J^ 

|l^ 

Is 

Date,  1896. 

3  — 

u 

C.G.S.  Heat- 
nsmitted  pe 

11 

°t 

j.S.  Heat-U 
lare  Centem 
Minute 

mperature  o 
Surface  in 

P 

irence  of  Tei 
een  Upper  : 
Surfaces  in 

ration  of  Kx] 

Condition  of 
Surface. 

H 

2 

.  C/) 

3* 

H 

i! 

3 

Q 

Feb.    20    ... 
Jan.    31       1 

887-0 

6,581 
6,698 

14-3 
i4-6 

62-96 
63-57 

104-9 

108-4 

135-0 
I36-0 

3o-o 
27-6 

20'O 
26'O 

Clean    Surface 
throughout. 

Feb.     7      I 

869-0 

6,287 

137 

59-67 

107-0 

i34'5 

27-5 

34'0 

Jan.    27    ... 

860-0 

6,172 

13-4 

58-58 

105-6 

130-3 

24-7 

21-0 

Feb.   21      I 

854-0 

6,219 

13-5 

59-03 

105-5 

132-0 

26-6 

2O'O 

„       10      ... 

844-0 

4,903 

10-7 

46-54 

1067 

126-0 

19-3 

25-0 

Jan.    16    ... 

825-0 

4,290 

9-3 

40-72 

105-5 

125-0 

19-5 

I4-0 

Feb.     3      I 

82O'O 

4,4io 

9-6 

41-86 

108-0 

127-0 

19-0 

26"0 

„      21       II 

776-0 

4,7ii 

10'2 

44-71 

105-5 

126-6 

2I-I 

21'0 

Jan.    30      I 

747-0 

3,44i 

7H9 

32-66 

107-0 

123-8 

16-8 

34'5 

„     30     II 

710-0 

3,208 

6-98 

30-45 

106-5 

121-3 

14-8 

I9-0 

Feb.     3     II 

700-0 

2,009 

6-33 

27-61 

106-2 

119-4 

13-2 

32-0 

Jan.    31     II 

660-0 

2,521 

5^9 

23-93 

107-0 

118-8 

n-8 

34'0 

Feb.   21  111 

660-0 

2,945 

6-41 

27-95 

104-1 

118-5 

14-4 

25-5 

,,      7    II 

584-0 

2,119 

4-61 

20'II 

104-4 

114-6 

IO"2 

32-5 

Jan.    29    ... 

781-5 

4,315 

938 

40-96 

107-5 

128-0 

20'5 

25-5 

TABLE  XLIV.— STEEL  PLATE.     THICKNESS,  256  CENTIMETRES. 
AREA,  105-4  SQUARE  CENTIMETRES. 


Date,  1896. 

'emperature  of  Hot 
Wall  in  °  C. 

.S.  Heat-Units  Trans- 
mitted per  Minnte. 

of  Water  Evaporated. 
Square  Foot  per  Hour 

C  S.  Heat-Units  per 
uare  Centemetre  per 
Minute. 

mperature  of  Upper 
Surface  in  °  C. 

mperature  of  Lower 
Surface  in  °  C. 

;rence  of  Temperature 
•een  Upper  and  Lower 
Surfaces  in  °  C. 

ration  of  Experiment 
in  Minutes. 

Condition  of 
Surface. 

t-1 

O 
u 

&l 

U^ 

H 

ft 

i! 

3 

a 

Feb.    ii     11 

927-0 

10,644 

23-1 

IOI'03 

107-0 

I54-0 

47-0 

9.0 

Smoked. 

„     ii  HI 

87I-0 

8,944 

19-5 

84-89 

107-2 

I45-4 

38-2 

9'5 

„     ii       I 

834-0 

7,732 

16-8 

73-39 

108-2 

142-2 

34'o 

22'O 

„ 

„       12      II 

656-5 

4,507 

9'5 

42-78 

105-8 

128"! 

22-3 

27-5 

„ 

..       12         I 

603-0 

3,755 

8-2 

35-69 

105-0 

123-0 

18-0 

20-5 

II 

June  8        1 

815-0 

7,366 

16-0 

69-90 

106-7 

136-7 

30-0 

23-0 

„ 

„      8     11 

753'Q 

6,158      1335 

58-42 

IO6'2 

I33-5 

273 

9-0 

„ 

„      8  III 

622-Q 

3,715        8-05 

35-24 

105-0 

121-6 

16-6 

23-0 

" 

THE  MODERN  STEAM  BOILER. 


183 


TABLE  XLV.— COPPER  PLATE.    THICKNESS,  0904  INCH  =  23  CENTIMETRES. 
AREA,  963  SQUARE  CENTIMETRES. 


t-Units 

:r  Minute. 

evaporated 
t  per  hour. 

Jnits  per 
netre  per 

Sj 

s 

s« 

-0°r 

:mperature 
and  Lower 
n»C. 

tperiment 
tes. 

Date,  1895. 

C.G.S.  Hea 

.nimitted  pe 

of  Water  1 
Square  Foo 

III 

CJ   3 

m  perature 
Surface  ii 

:mperature 
Surface  ii 

erence  of  T« 
teen  Upper 
Surfaces  i 

wg 

o~ 
1  "     ' 

Condition  of 
Surf  ice. 

S 

sl 

* 

H 

H 

si 

* 

Oct.    25      I 

10,070 

24-0 

104.6 

108-0 

1223 

14-3 

I2'5 

Smoked. 

„     25    II 

11,840 

28-2 

I23-0 

109-0 

1233 

I4'3 

II'O 

H 

„       25    III 

13,810 

32-8 

I43'4 

108-6 

I22'0 

I3'4 

II'O 

„ 

,,       24        I 

"4.430 

34'3 

I49-9 

IO6'3 

I24-O 

17-7 

47-0 

„ 

,,       22         I 

9,560 

22-7 

99'3 

I05-7 

II8-6 

12-9 

29-0 

Not  smoked. 

„       22       II 

6,550 

15-6 

68-0 

104-9 

114-6 

9'7 

12-5 

(( 

„        21          I 

10,680 

25-4 

1  10-8 

107-8 

U9-8 

12-0 

iro 

Smoked. 

„       21       II 

4,700 

1  1  '2 

48-9 

io6x> 

II2-3 

6-3 

40-0 

M 

„        17      - 

12,110 

28-8 

125-7 

107-0 

118-1 

in 

300 

M 

„      16     ... 

9,590 

22-8 

99-6 

105-0 

114-8 

9-8 

36-0 

„ 

July    23     ... 

15,320 

36-4 

I59-0 

104-6 

1  20-  1 

15-5 

12'0 

M 

„      23       I 

14,140 

33-6 

146-8 

106-2 

119-0 

12-8 

I4-0 

H 

„      23     II 

16,050 

38-2 

166-7 

106-5 

I20'6 

14-1 

IO'O 

M 

„   25    I 

15-040 

35-8 

156-1 

105-4 

118-7 

13'3 

23-0 

„ 

„   25  II 

... 

... 

107-1 

121-9 

14-8 

22-0 

•• 

C.O.S  HtAT  ONITS  TRANSMITTED  PER  SQ  CM  PER  MINUTE  THROUGH  PLATE 
CURVES  8HOWLNQ  THE  VARIATION  OF  HEAT  TfiANSMISSION  WITH  THE 
TEMPERATURE  OP  THE  HOT  WALL. 

FIG.  89. 


1 84 


THE  PRACTICAL  PHYSICS  OF 


The  curves  in  diagrams  Figs.  89  and  90  have  been  plotted 
from  these  results,  and  the  following  are  the  remarks  of  Miss 
Bryant  on  them  :  "In  Figs.  89  and  90  parabolas  are  drawn 
passing  nearly  through  the  points  representing  the  results  given 
in  Tables  XLL,  XLII.,  and  XLIII.  and  XLIV.  respectively. 
It  will  be  seen  that  all  the  results  follow  nearly  the  parabolic  law 

£H  =  (T-ioo)2 

where  H  is  the  number  of  heat  units  transmitted  per  square 
centimetre  per  minute,  and  T  the  temperature  of  the  hot  wall  in 
degrees  Centigrade. 

"  A  comparison  of  the  curves  in  Fig.  89  shows  that,  when  both 
surfaces  are  blackened,  for  the  same  temperature  of  the  hot 
wall  the  evaporation  through  the  steel  plate  was  greater  than 
that  through  the  copper,  and  thus  the  superior  conductivity  of 
the  latter  gives  it  no  appreciable  advantage  in  this  respect. 
With  surfaces  covered  with  oxide  the  effects  are  nearly  the 
same  for  the  two  plates,  and  the  evaporation  in  both  cases  is 
much  less  than  with  blackened  surfaces. 


10  *O  BO  BO  IOO  120 

HEAT    UNITS    TRANSMITTED     PER     59      C  M      PER.    MINUTE 


FIG.   90. 


THE  MODERN  STEAM  BOILER.  185 

<4A  comparison  is  afforded  in  Fig.  90  between  the  effects  of  a 
clean  and  of  a  blackened  surface  exposed  to  radiation.  Irregu- 
larities in  the  clean  surface  have  caused  the  results  to  be  some- 
what irregular,  but  it  will  be  seen  that,  while  those  for  the 
blackened  surface  follow  very  nearly  the  parabolic  law,  those  for 
the  clean  surface  deviate  considerably  from  it.  In  every  case 
the  evaporation  increases  somewhat  more  rapidly  than  it  would 
if  the  parabolic  law  were  exactly  followed,  and  the  author  rinds 
that  Mr.  Blechynden's  results  deviate  from  this  law  in  an  exactly 
similar  way,  although  the  mode  of  heating  and  the  methods  of 
measurement  which  he  adopted  were  very  different  from  those 
now  described.  With  a  blackened  surface  the  heat  is  almost 
entirely  supplied  by  radiation,  and  the  curve  is  very  nearly  a 
parabola.  With  a  clean  surface  the  heat  supplied  by  convection 
becomes  relatively  more  important,  and  the  deviation  from  the 
parabola  is  increased.  An  experiment  arranged  so  that  the  hot 
gases  acted  directly  on  the  plate  showed  a  deviation  from  the 
parabolic  law  in  the  same  direction  and  of  very  much  greater 
amount.  A  possible  explanation  of  this  is  that  while  the  heat 
gained  from  radiation  is  proportional  to  the  square  of  the  differ- 
ence of  temperature  between  the  surfaces,  that  clue  to  convec- 
tion is  more  nearly  proportional  to  a  higher  power  of  this 
difference.  Attempts  to  measure  precisely  the  actual  temperature 
of  the  gas  when  it  strikes  the  plates  were  not  successful.  Any 
temperature  between  the  highest  in  the  furnace  and  one  very 
near  that  of  the  surface  of  the  plate,  i.e.,  about  160°  C.  could  be 
obtained  by  placing  a  junction  at  different  positions  in  the  hot  gas, 
and  it  was  evident  there  was  a  layer  of  cold  gas  next  the  plate. 

"  A  curious  effect  was  noticed  during  the  experiments.  On 
several  occasions  when  the  vessel  boiled  dry,  a  sudden  fall  of  the 
temperature  of  the  plate,  especially  near  its  upper  surface,  occurred, 
followed  by  a  rapid  rise.  The  cooling  is  evidently  due  to  rapid 
evaporation  taking  place  when  the  water  is  nearly  boiled  away,  and 
is  followed  by  a  rise  of  temperature  as  soon  as  the  surface  is  dry." 
These  remarks  confirm  the  opinion  that  in  Mr.  Blechynden's 
experiments  the  effects  of  convection  in  the  heating  were  absent, 
on  account  of  the  impossibility  of  a  proper  circulation  of  the  gases 
taking  place  in  contact  with  the  metal  plate,  and  they  show  that  if 
heating  by  convection  had  been  properly  carried  out,  the  "  para- 
bolic law  "  would  not  have  applied  to  his  experimental  results. 


186  THE  PRACTICAL  PHYSICS  OF 

The  "  layer  of  cold  gas  next  the  plate  "  points  to  the  fact 
that  the  circulation  of  the  hot  gases,  in  the  case  of  Miss  Bryant's 
experiment,  was  not  sufficiently  rapid.  Some  experiments  were 
also  made  on  the  effect  of  oil  on  the  water  surface  of  the  con- 
ducting plate,  but  the  results  obtained  were  not  remarkable. 
The  comparison  made,  however,  between  the  fusible  plug  method 
and  the  thermo-junction  method  of  measuring  temperatures 
is  of  some  importance.  Plugs  and  thermo- junctions  were 
inserted  in  the  same  plate,  and  their  temperature  indications 
were  compared  and  found  to  be  as  follows  : — 

Temperature  of  Lower  Surface  of  Plate. 


By  Thermo-junctions. 


By  Fusible  Plugs. 


123-5°  c. 

130-0°  C. 


About  123°  C. 

Between  139°  C.  and  149°  C 
Above  161°  C. 


Not  only  was  it  found  that  the  fusible  plugs  gave  records 
which  were  not  consistent  with  themselves,  by  melting  at 
different  temperatures,  but  also  they  invariably  showed  a  higher 
temperature  than  that  of  the  plate. 

For  this  reason  the  results  of  Sir  A.  (then  Mr.)  Durston's  ex- 
periments are  not  here  quoted  in  detail,1  although  they  possess 
considerable  interest,  but  chiefly  in  connection  with  the  fire-tube 
class  of  boilers.  It  is  extremely  difficult  to  ensure  a  sufficient 
supply  of  water  to  the  surfaces  of  flat  tube  plates,  either  vertical 
or  horizontal,  which  hold  a  number  of  tubes  through  which 
flame  and  hot  gas  are  passing — the  same  hot  gases  and  flame 
also  striking  against  the  tube  plate.  There  is  a  similar  difficulty 
in  getting  an  adequate  circulation  of  water  on  the  surfaces  of 
the  inner  rows  of  horizontal  fire  tubes,  especially  those  nearer 
the  top,  as  the  steam  generated  below  must  pass  around  these 
on  its  escape  upwards.  Hence,  no  doubt,  flame  tubes  must 
become  hotter  than  water  tubes,  and  that  either  they  or  the  flat 
tube  plates  become  too  hot  for  durability  of  tube  joints,  experi- 
ment and  practice  both  show. 

Zittenberg's  Experiments. — Mr.  Zittenberg2  made  similar  experi- 
ments to  some  of  Mr.  Durston's,  but  measured  the  temperature 

1  They  will  be  found  recorded  in  Chap.  II.       2  See  Engineering,  Vol.  lv.,  p.  440 


THE  MODERN  STEAM  BOILER.  187 

of  the  plate  by  maximum  thermometers  dipped  in  holes  tapped 
almost  through  the  whole  thickness  of  the  plate  and  filled  with 
quicksilver.  He  found,  with  4^  inches  of  blast  pressure  on  the 
hre,  "  an  excess  of  14^°  C.  at  a  steaming  power  of  35  Ibs.  per 
square  foot,  against  an  excess  of  44°  C.  to  68°  C.  in  the  two 
experiments  of  Mr.  Durston  with  a  J-in.  steel  plate."  No  such 
differences  as  the  latter  should  be  found  in  the  metal  of  properly 
constructed  water-tube  boilers  at  work. 

Experiments  on  a  Xicltiussc  Water-tube  Boiler. — The  most 
recent  experiments  of  a  similar  kind  to  the  foregoing,  and 
probably  the  only  ones  hitherto  made  with  a  water-tube  boiler, 
are  those  carried  out  by  the  Messrs.  Niclausse  on  one  of  their 
boilers,  and  fully  reported  in  a  paper  read  at  the  Congres 
cle  Mecanique  at  Paris  in  1900.  The  boiler  was  composed  of 
twelve  rows  of  steel  tubes,  having  in  each  row  10  tubes  of 
3*23  ins.  (or  82  mm.)  external  diameter,  and  6*35  feet  (or  1*94  m.) 
long.  The  external  surface  of  each  row  was  53*8  square  feet 
(or  5  sq.  metres)  and  the  total  heating  surface  of  the  boiler  was 
53-8  x  12  =  645  square  feet  (or  5  x  12  =  60  sq.  metres).  The  grate 
area  was  21*5  sq.  feet  (or  2  sq.  metres)  and  the  ratio  of  total 
heating  surface  to  grate  area  was  30  to  i.  The  internal  circulating 
tubes  were  each  i  j9,.  inch  (or  40  mm.)  diameter. 

For  these  experiments  each  horizontal  row  or  storey  (etage)  of 
tubes  was  provided  with  distinct  upcast  and  downcast  passages 
to  the  steam  and  water  drum  and  with  a  separate  feed  pipe,  and 
the  evaporation  from  each  row'  was  measured  separately,  the 
rows  being  numbered  from  i  to  12  upwards,  beginning  with  the 
row  immediately  over  the  fire.  The  calorimetric  value  of  the 
coal  used  was  12-91  Ibs.  of  water  evaporated  from  and  at  212°  F. 
per  Ib.  of  coal  and  in  each  of  the  trials  (lasting  about  eight 
hours  each)  nine  different  rates  of  combustion  per  square  foot 
of  grate  with  the  same  coal  were  employed,  beginning  with  a 
minimum  of  10  Ibs.  and  going  on  to  a  maximum  of  60  Ibs.  per 
square  foot  of  grate  per  hour.  The  steam  was  evaporated  in 
all  the  trials  at  atmospheric  pressure  from  a  feed- water  tempera- 
ture of  32°  F.  (or  11°  C.).  Both  coal  and  water  were  carefully 
weighed,  but  neither  the  temperature  nor  the  composition  of  the 
escaping  gases  was  examined,  the  tests  being  merely  to  deter- 
mine the  relative  amounts  of  evaporation  from  each  row  or 
storey  of  tubes  at  the  different  rates  of  combustion. 


i88 


THE  PRACTICAL  PHYSICS  OF 


•/OOOI  T*l                    ^     !„» 

VJ 

" 

tu 

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S  *! 

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b 

It 

,,M 

<•?                  "a  • 
tt 

Is 

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°*  *2? 

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.Jst 

w  *d 

r^        s        S-        S 


THE  MODERN  STEAM  BOILER.  189 

The  following  were  the  rates  of  combustion  employed  : — 

50  75  100  125  150  175  200  250  300  kilos  of  coal  per  sq. 
metre  of  grate  surface  per  hour,  or 

10  15  20  25  30  35  40  50  60  Ibs.  coal  per  sq.  ft.  grate 
surface  per  hour. 

A  remarkable  feature  of  the  results  is  found  in  the  fact  that 
the  percentage  of  the  total  evaporation  yielded  by  each  of  -the 
twelve  rows  remained  the  same,  whether  10  Ibs.  or  60  Ibs.  of  fuel 
were  burned  per  square  foot  of  grate  area  per  hour.  This 
showed  that  the  relative  value  of  each  row  for  evaporation  was  a 
fixed  quantity. 

The  results  are  set  out  in  the  curves  in  diagram,  Fig.  91, 
which  gives  the  plotted  results  of  evaporation  from  each  row  in 
percentage  of  the  total  evaporation  from  the  twelve  rows.  The 
first  three  rows  nearest  the  fire,  with  161  sq.  feet  of  heating 
surface,  gave  47*94  (nearly  50)  per  cent,  of  the  total  evaporation 
from  645  sq.  feet  ;  the  remaining  52*06  per  cent,  required  three 
times  that  amount  of  surface  as  provided  by  the  remaining  nine 
rows.  Diagram  Fig.  92  gives  the  evaporative  rates  for  each  row 
of  tubes  in  Ibs.  of  water  per  sq.  foot  of  heating  surface  per  hour 
for  the  nine  different  rates  of  combustion,  the  vertical  scale 
representing  the  pounds  of  water  evaporated  and  the  horizontal 
the  number  of  each  row  of  tubes.  The  first  row,  nearest  the 
fire,  evaporated  from  a  minimum  of  8J  Ibs.  of  water  per  square 
foot  of  heating  surface  per  hour  to  a  maximum  of  34^  Ibs.  ; 
whilst  the  twelfth  row  evaporated  only  from  i^  Ib.  to  a  maximum 
of  6  Ibs.  per  square  foot  per  hour. 

Diagram  Fig.  93  shows  the  heat  efficiency  for  each  row  of 
tubes  and  for  the  different  rates  of  combustion.  The  vertical 
scale  on  the  left  gives  Ibs.  of  water  evaporated  per  Ib.  of 
coal,  and  that  on  the  right  the  percentages  of  heat  efficiency, 
whilst  the  horizontal  scale  shows  the  numbers  of  the  rows 
of  tubes.  The  curves  give  the  results  for  the  different  rates  of 
combustion  in  Ibs.  of  coal  per  square  foot  of  grate.  The 
100  per  cent,  line  coincides  with  the  calorific  value  of  the 
coal.  It  is  apparent  that  the  lowest  rate  of  combustion, 
viz.,  10  Ibs.  per  square  foot  of  grate  area  per  hour,  gives  the 
highest  heat  efficiency  with  this  boiler,  and  that  the  efficiency  is 
lowest  at  the  highest  rate  of  combustion. 

Diagram    Fig.  94   gives   the   plotted    results  on    a  base 


190  THE  PRACTICAL  PHYSICS  OF 

of  Ibs.  of  water  evaporated  per  square  foot  of  heating  surface 
per  hour,  with  the  heat  efficiencies  of  the  boiler  as  a  vertical 
scale.  In  this  way  the  efficiencies  can  be  read  off  and  com- 
pared with  different  evaporative  results.  The  curves  represent 


Plotted  Lxperimonlal  {.vaporbhve  results  /or  eacn  row  Tubes 
Ibs.  Wa^r  E.v»porat*a  p  Hr  p  fq  S+of  HeaHnq  Surface 
\Hor,zonlals       /V*t>r'  Rows   of  Tubas 
for  9  difC1'  r-af*s  of  Combustion  60  to  HJ.'hs  CiMj  p  Sq  f'  Crab 

or',Tub»s  £  10 in  <wc/>  row  -  120  TuDea 
£>folrria/  Diameter  xll  Tubas  j'2"j"-  82  m/m 

14   M»f,-*,  ' 


FIG.  92. 


the  results  obtained  from  the  different  rows  of  tubes  and 
for  the  different  rates  of  combustion.  The  dotted  lines  to 
the  left  are  assumed  so  that  at  zero  evaporation  there  will 
be  zero  efficiency. 

The   general  result  with  this  boiler  is  that  all  the  lines   of 


THE  MODERN  STEAM  BOILER. 


191 


heat  efficiency  decrease  with  the  higher  rates  of  combustion, 
and  are  lowest  with  the  highest  rates  of  evaporation.  The 
experiments,  however,  show  that  an  evaporation  of  34  Ibs. 


Plot**}  £j,nonmontel  Results  with  Htal  efficiency  for 

ch  K0»  of  Tvtts  A  for  9  fiafos  of  C 
60  fo  10  Ibt  p  Sq  f  p  Hr 


iJ^***  lbs  War*r  Evaporated  o  it>  Coa: 
Horitonfgl   H'  of  Rt}»3  of  Tubes 


FIG.  93. 


of  water  per  square  foot  of  heating  surface  per  hour  is  obtained 
without  injury  to  the  tubes. 

Row's   Experiments. — The   experiments    carried   out    by   Mr. 
O.    M.    Row,    and    communicated   by  him  to    the    Manchester 


192  THE  .PRACTICAL  PHYSICS  OF 

Association  of  Engineers  (^yth  February,  1897),  show  the 
remarkable  effects  of  the  indentations  of  the  "  Row "  tube 
upon  the  efficiency  of  heat-transmitting  surface.  In  several 
experiments  the  time  required  to  transmit  a  given  amount 
of  heat  from  steam  to  water  was  one-half  of  that  required 
in  the  case  of  plain  cylindrical  tubes  of  exactly  the  same  heating 
surface.  In  order  to  ensure  the  employment  of  the  same 
area  of  heating  surface,  the  same  tubes,  which  had  first  been 
tested  as  plain  tubes,  were  afterwards  indented  and  then 
tried  under  identical  conditions  in  their  new  form. 

The  increased  effect  has  been  ascribed  to  a  "  scouring 
action  "  due  to  the  form  of  the  indented  tube,  which  prevented 
the  adherence  of  steam  bubbles  to  the  surface,  and  whilst 
that  is  probably  true  there  seems  little  doubt  that  additional 
velocity  is  imparted  to  the  movement  of  the  currents  in 
consequence,  not  only  of  frequent  changes  of  direction,  but  also 
of  the  fluids  being  compelled  to  assume  the  form  of  com- 
paratively thin  films  in  contact  with  the  heating  surfaces. 

Movement  of  Hot  Gases. — Sir  A.  J.  Durston  made  a  series  of 
measurements  of  the  temperatures  at  various  points  in  the  travel 
of  hot  gas  in  a  flame-tube  boiler,  commencing  at  the  combustion 
chamber,  and  then  at  successive  intervals  of  length  inside  some 
of  the  tubes,  up  to  the  smoke  box.  These  measurements  were 
made  with  a  Le  Chatelier  electrical  pyrometer  and  are  shown  in 
the  following  Table  and  curve  (Fig.  95),  which  gives  the  mean 
results  of  eight  sets  of  records. 


THE  MODERN  STEAM  BOILER. 


193 


TABLE  XLVI. 


Temperature  in  combustion  chamber 
,,  just  inside  tube 

,,  in  tube  I  inch  from  combustion  chamber 

..       2 

»»  ))  3  ))  M  M 

H  »         4  M  M  M 

M  n       5          )»  i)  11 


M  I  ft-  2  ins. 

II      I       11*       II 

„  2  „  8  „ 
n  3  ii  8  ,, 
M  4  n  8  ,, 
>i  5  i>  8  „ 
n  °  n  8  „ 
in  smoke  box 


Degrees 
Fahr. 

1644 
1550 
1466 
1426 

1405 
1412 

1398 
1406 
1400 
1410 
1368 

1295 
IIQS 

1106 

1015 

926 

887 

782 


.  95- 


i94 


THE  PRACTICAL  PHYSICS  OF 


Another  curve,  slightly  different  in  form,  will  be  found  recorded 
in  Sennett  &  Gram's  work  "  On  the  Marine  Steam  Engine" 
(Fig.  15,  p.  41)  ;  see  also  Fig.  96.  The  boiler  used  in  these 
experiments  was  the  ordinary  marine  Scotch  or  cylindrical  boiler 
in  Keyham  Yard.  It  had  two  furnaces  (3ft.  6in.  diameter)  and  166 
return  tubes  2|ins.  outside  diameter  and  6ft.  Sin.  long,  measured 
to  the  outsides  of  the  tube  plates.  The  boiler  was  worked  at  its 
normal  capacity,  the  consumption  of  coal  being  about  17  Ibs.  per 
square  foot  of  grate.  Sir  A.  ].  Durston's  Paper  contains  no  infor- 
mation as  to  the  quantity  of  hot  gases  escaping  per  minute,  but  as 
on  a  total  grate  area  of,  say,  46  square  feet,  there  were  46  x  17  = 
782.  Ibs.  of  coal  burned  per  hour, 
or  7-/Q?  =  13*2  Ibs.  burned  per  minute, 
on  the  supposition  that  18  Ibs.  of  air 
were  supplied  per  Ib.  of  coal,  we 
can  arrive  at  an  idea  of  the  volume 
and  velocity  of  the  gases  by  means 
of  Rankine's  rule,  quoted  in  Chap. 
III.,  p.  63.  The  total  area  of  the 
return  tubes  at  2\  ins.  inside  diameter 
was  4-9087  x  1 66  =  814-84  square 
inches,  and  therefore  it  appears 
that,  taking  the  temperature  of  the 
gases  at  either  the  highest  or  the 
lowest  temperature  in  the  tubes,  the 
velocity  in  feet  per  second  must 
have  been  very  low  (apart  from 
their  probably  being  throttled  by 
the  pyrometer  in  the  tubes  actually 

tested),  and  on  that  account  the  transmission  of  heat  must  have 
been  at  a  low  rate  also.  Moreover,  the  tube  surface  in  this  form 
of  boiler  is  robbed  of  its  efficiency  by  being  placed  right  in  the 
path  of  all  the  steam  generated  from  the  surface  of  the  furnaces. 
The  Table  also  shows  that  the  gases  did  not  flow  through 
the  tubes  in  straight  steam  lines,  undulations  of  temperature 
being  recorded  at  from  three  to  four  inches,  five  to  six  inches, 
and  seven  to  eight  inches. 

It  has  been  ascertained  from  investigations  of  the  movement 
and  velocity  of  chimney  gases,  that  the  motion  of  hot  gases, 
while  proceeding  along  passages  which  introduce  the  elements 


FIG.  96. 


THE  MODERN  STEAM  BOILER.  195 

of  friction  and  of  changes  of  temperature,  assumes  the  form  of  a 
spiral  vortex.  The  vortex  movement  may  also  be  seen  when 
either  heated  gas  or  steam  is  allowed  to  escape  into  a  cooler 
atmosphere.  It  has  often  been  noticed  that  the  smoke  escaping 
from  the  top  of  a  tall  chimney  moves  not  in  straight  lines, 
but  in  curls,  which  have  the  shape  of  vortices.  See  Fig.  97. 
Combined  with  this,  in  Mr.  Mactear's  results !  the  point  of 
greatest  speed  was  found  at  a  less  distance  from  the  out- 
side of  a  flue  or  chimney  than  one-third  of  the  radius,  which 
Peclet  indicated  as  the  point  of  greatest  speed.  It  would  follow 
from  this  that  by  adopting  a  spiral  form  of  flues  or  passages  for 
the  hot  gases,  there  would  be  no  difficulty  in  obtaining  sufficient 
movement  to  prevent  any  stagnation  of  gases  at  the  surfaces  of 
the  tubes. 

"Layers  "  of  Gases. — The  idea  of  a  layer  of  cold,  or  rather  of 
cooled,  gases  adhering  to  the  heating  surface  of  boilers,  advanced 
by  Miss  Bryant  and  other  investigators,  is  contrary  to  known  laws 
of  the  diffusion  of  gases.  If  cooled  gases  are  delayed  by  eddies 
or  otherwise  in  contact  with  the  metal,  long  enough  to  interfere 
appreciably  writh  heat  transmission,  this  only  shows  that  greater 
movement  or  agitation  of  the  gases  is  what  is  wanted.  For 
philosophic  discussion  of  the  subject  of  heat  transmission 
between  gases,  solids,  and  liquids,  it  may  be  advisable  to  imagine 
a  series  of  layers  of  almost  infinitesimal  thinness,  as  has  been 
done  by  Fourier  and  by  Lord  Kelvin,  and,  following  them,  in 
Mr.  Halliday's  recent  paper.2  But  there  is  danger  in  allowing 
such  a  "  mental  picture "  to  occupy  the  place  and  attain  the 
importance  of  an  acknowledged  fact.  It  must  not  be  forgotten 
that  in  this  matter  we  are  dealing  with  molecular  vibrations  of 
some  sort  (about  which,  however,  we  know  very  little  beyond 
the  fact  that  there  are  such  vibrations)  passing  through  different 
media  which  are  in  intimate  contact  with  one  another.  In 
traversing  media  with  different  degrees  of  molecular  mobility — 
such  as  solid,  liquid,  and  gas — there  are  probably  differences  in 
the  period  of  the  vibrations,  or  therfe  is  a  period  peculiar  to  each 
substance,  and  the  change  from  one  period  or  frequency  to 

1  See  Mills  and  Rowan  "  On  Fuel  and  its  Applications,"  pp.  379,  380  ;  also 
Reports  on  the  Examination  of  Chimney  Gases,  Alkali  Manufacturers'  Associa- 
tion, 1876-1877. 

2  Trans.  Inst.  Engineers  and  Shipbuilders  in  Scotland,  Vol.  xlii.  p.  41. 

H  2 


196  THE  PRACTICAL  PHYSICS  OF 

another  may  introduce  some  resistance  or  loss.  But  if  the 
movement  can  be  transmitted  through  a  comparatively  rigid  body, 
like  iron,  with  an  almost  inappreciable  resistance,  it  ought  to  be 
possible  to  transmit  vibrations  of  the  same  nature  between 
different  substances  in  intimate  contact  without  any  considerable 
loss.  It  is,  however,  urged  that  "  a  film  of  cooled  gases  "  does 
not  correctly  describe  the  state  of  affairs.  "  Was  it  not  better  to 
say,"  said  one  author,  "  the  adhesive  film  almost  infinitesimally 
thin,  varied  in  temperature  from  the  temperature  of  the  plate 
on  one  side  to  that  of  the  gases  on  the  other,  which  would 
probably  be  from  400°  to  2500°  F.  in  the  thickness  of  a  bit  of 
paper."  But  this  really  alters  the  matter  very  little,  because  in 
it  there  is  an  "  adhesive  film  "  which  has  the  temperature  of  the 
plate  at  one  face,  whilst  immediately  outside  of  that  there  may 
be  a  temperature  2000°  higher.  That  is  certainly  a  very  near 
approach  to  "  a  film  of  cooled  gases  " — it  merely  alternates  the 
film,  but  not  the  idea.  There  are,  however,  some  explanations 
given  to  us  :  "  Although  there  is  an  adhering  film  of  gas  it  is  not 
quite  evident  that  the  same  particles  of  gas  will  form  that  film. 
It  is  hardly  to  be  expected  that  this  will  be  so,  when  there 
is  constantly  rolling  against  this  film  of  gas,  gas  of  the  same 
kind  greatly  agitated.  The  fire  side  of  the  film  will  hardly  be 
defined,  there  may  be  breaches  into  it,  and  there  will  be  diffusion, 
and  if  the  theory  of  heat  is  correct,  there  will  be  a  constant 
interchange  of  particles.  That  being  so,  and  the  velocity  of  the 
particles  being  as  the  square  of  the  temperature,  there  will  be 
an  average  effect  which  should  be  greater  than  that  expected 
from  a  simple  rise  of  temperature." 

It  will  certainly  occur  to  many  that  there  is  no  reason  why  the 
diffusion  by  interchange  of  particles  should  have  an  arbitrary 
limit,  and  why  the  fresh  particles  of  gas  should  not  "  roll 
against "  the  metal  surface  itself  instead  of  stopping  at  the 
"  adhering  film  "  which  only  consists,  after  all,  of  gas  of  the  same 
kind  as  that  which  is  "  rolling."  If  the  rolling,  or  interchange 
of  particles,  or  diffusion,  proceeds  as  far  as  we  maintain  it  does, 
that  is,  as  far  as  the  walls  of  the  chamber  confining  the  gas, 
there  is  then  no  probability  of  the  existence  of  u  an  adhesive 
film  "  of  gas,  and  the  only  valid  explanation  of  slow  conduction  of 
heat  from  hot  gases  to  metal  is  that  of  slowness  of  movement  of 
the  gases — always  adding  the  possibility  of  resistance,  due  to 


THE  MODERN  STEAM  BOILER.  197 

alteration  of  the  frequency  of  vibrations.  The  same  view  holds 
good  as  to  the  water  side  of  the  plate,  but  because  the  rate  of 
movement  required  for  the  water  is  not  so  great  as  that  required 
for  gases,  better  results  have  been  reached  with  it,  as  we  have 
seen.  The  good  results  obtained  with  steam  as  the  heating 
agent,  instead  of  lire  gases,  may  be  accounted  for  on  similar 
grounds.  It  has  been  possible  to  reach  with  ordinary  apparatus 
the  velocity  required  by  the  steam,  this  being  less  than  that 
required  by  highly  heated  and  therefore  expanded  gases  of  less 
specific  heat  and  less  density  than  the  steam. 

Diagrams  such  as  the  one  published  by  Mr.  JHalliday  ("  Steam 
Boilers,"  p.  50,  rig.  20),  or  the  one  shown  by  Professor  Watkinson 
(Trans.  lust.  Engineers  and  Shipbuilders  in  Scotland,  Vol.  xli., 
pp.  58,  59),  are  misleading,  because  they  do  not  properly  represent 
the  actual  facts.  (See  also  Trans.  Inst.  Engineers  and  Ship- 
builders, Vol.  xli.,  p.  130.) 

There  is  not  a  loss  of  heat  corresponding  to  the  drop  of 
temperature  represented  by  the  diagrams,  nor  is  that  drop  a 
proof  of  great  resistance.  Apart  from  the  great  difficulty  of 
correctly  measuring  the  changes  of  temperature  in  the  portions 
of  gases  or  water  immediately  beside  the  iron  surfaces,  the 
diagrams  cannot  discriminate  between  the  quantity  of  heat 
passing,  and  the  actual  temperature  at  the  point  measured.  It 
has  been  shown  by  M.  Hirsch  that  an  evaporation  of  75  Ibs.  of 
water  per  square  foot  of  surface  per  hour  need  not  cause  a 
difference  of  temperature  between  the  surfaces  of  the  plate  of 
more  than  300°  F.  even  with  his  apparatus,  and  an  evaporation 
of  140  Ibs.  per  square  foot  per  hour  has  been  carried  on  with  a 
difference  of  only  107°  F.1  under  specific  conditions.  The  truth 
is  that  the  actual  temperature  of  the  metal  is,  practically,  a 
static  condition,  whilst  the  flow  of  heat  is  a  dynamic  process 
and  the  diagram  cannot  properly  represent  both.  Regarding 
these  differences  of  temperature,  Lord  Kelvin  has  said  (Article 
"  Heat  "  Encycl.  Brit.,  9th  Edtn.),  "  Although  the  water  or  air 
at  the  very  interface  of  its  contact  with  the  metal  is  essentially  at 
the  same  temperature  as  the  metal,  there  must  be  great  diffe- 
rences of  temperature  in  very  thin  layers  of  the  fluid  close  to  the 

1  This  was  the  temperature  difference  between  steam  (used  for  heating)  and 
water,  and  therefore  that  of  the  iron  surfaces  could  not  have  been  so  high. 
(See  Table  at  p.  138).  Compare  also  Professor  Wit/'s  result  on  p.  216  following. 


198  THE  PRACTICAL  PHYSICS  OF 

interface  when  there  is  a  large  flux  of  heat  through  the  metal,  and 
the  temperature  of  the  fluid,  .as  measured  by  any  practicable 
thermometer,  or  inferred  from  knowledge  of  the  average  tem- 
perature of  the  whole  fluid,  or  from  the  temperatures  of  entering 
and  leaving  currents  of  fluid,  may  differ  by  scores  of  degrees 
from  the  actual  temperature  of  the  solid  at  the  interface."  As 
the  commencement  and  ending  of  these  remarks  are,  however, 
in  apparent  conflict,  it  is  probable  that  Lord  Kelvin  meant  at 
starting  to  say  that  portions  of  the  fluid  were  momentarily  at  the 
temperature  of  the  iron  at  the  surface.  The  fact  that  both  gases 
and  water  are  in  rapid  motion  (the  more  rapid  the  better)  would 
prevent  the  arrangement  of  either  into  "layers,"  the  actual 
formation  of  which  would  demand  totally  different  conditions. 
It  is  important  that  Lord  Kelvin  admits  that  the  temperature 
of  the  fluid  may  differ  by  scores  of  degrees  from  the  actual 
temperature  of  the  solid  at  its  surface  when  there  is  a  large  flux 
of  heat  through  the  metal. 

Comparison  of  Heat  Transmission  with  Electrical  and  Magnetic. 
— Perhaps  the  clearest  view  of  the  action  is  afforded  by  a  com- 
parison with  the  analogous  cases  of  electricity  and  magnetism. 

p> 
It   is   well  known  that  the  law  in  these  matters  is  C  =  ^  or 

,          ,.,   v        electromotive    force,  , 

current   (quantity)  =  -  or     tor     magnetism 

resistance  ; 

6  =  — ,  and,  as  in  the  case  of  heat  we  are  dealing  with  allied 
K 

molecular  vibrations,  it  is  reasonable  to   expect   that  the  con- 

rp <T«1 

ditions  here  should  be  similarly  expressed,  viz.,  Q  = 


, 

Q  being  the  quantity  of  heat  flowing,  measured  in  heat  units. 
T  — T1  being  the  difference  of  temperature  which   causes  the 

flow,  and  thus  answering  to  the  difference  of  potential 

in  the  electrical  circuit  ;  and 

R  being  the  sum  of  the  resistance  opposed  to  the  flow  of  heat. 
In  one  respect  such  heat  measurements  are  much  less  complete 
than  those  of  electricity,  and  that  is  in  the  fact  that  no  proper 
measure  or  expression  of  this  resistance  (to  correspond  to  the 
ohm  in  electrical  measurements)  has  been  as  yet  arrived  at. 
Consequently,  in  dealing  with  the  transmission  of  heat  in  boiling 
or  steam  raising,  the  conditions  of  the  action  have  been  variously 


THE  MODERN  STEAM  BOILER.  199 

expressed.  There  is  this  difference  between  the  action  here 
and  that  in  electrical  matters  that,  whereas  the  resistance  to  the 
flow  of  electrical  current  is  wholly  a  question  of  the  condition 
of  the  wire  or  metallic  current,  in  the  transmission  of  heat, 
resistance  may  be  due  to  the  condition  of  the.  metal  plate,  and 
also  may  be  in  great  part  due  to  the  want  of  proper  conditions 
in  the  fluids  which  form  part  of  the  circuit.  It  has  been 
customary  to  class  these  different  causes  of  resistance  under  the 
heads  of  the  internal  thermal  resistance  of  the  plate  and  the 
external  thermal  resistance,  but  to  confine  these  too  much  to  a 
question  of  the  plate  and  its  surfaces.  Rankine  says  :  "  The 
rate  of  external  conduction  may  be  expressed  by  dividing  the 
difference  of  temperature  by  a  coefficient  of  external  thermal 
resistance,  depending  on  the  nature  of  the  substances  and  also 
on  their  temperatures  "  ;  but  it  is  evident,  from  what  wre  have 
been  considering,  that  this  expression  must  also  be  made  to 
bear  some  relation  to  the  velocities  of  movement  where  air  or 
hot  gases,  or  steam  or  water,  are  concerned  in  the  action. 

The  difficulty  is  not  to  get  the  heat  to  pass  from  the  fluid  to 
the  iron,  or  vice-versa,  but  it  is  to  keep  the  fluids  in  the  best 
condition  for  the  maximum  flow  of  heat. 

Professor  Perry's  Formula. — Following  Professor  Osborne 
Reynolds'  theoretical  forecast,  Professor  Perry1  has  recently 
suggested  a  general  symbolic  representation  of  the  theory  of 
transmission  in  fluids.  Let  average  velocity  be  V,  average 
temperature  (absolute)  of  gases  be  T,  and  average  temperature 
of  metal  plate  be  T0.  Suppose  a  layer  of  fluid  at  rest  at  the 
surface  of  the  metal  of  a  flue.  Per  unit  area  per  second  let  N 
molecules  enter  this  layer,  giving  to  it  axial  momentum  per 

second  proportional  to  NV.     This  is  what  is  meant  by  force  of 

p 
friction  F  per  unit  area  ;  so  that  N  oc_. 

Now,  each  molecule  brings  with  it  kinetic  or  heat  energy 
proportional  to  T,  and  takes  away  energy  proportional  to  T0. 

Neglecting  heat  resistance  between  layer  and  metal,  the  heat 
per  second  per  unit  area  brought  to  the  metal  is  H  ocN  (T— T0) 

or      H«£(T-T0). 

1  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland.  Vol.  xlii.  Part  I., 
25  Oct.,  1898.  Prof.  Perry's  remarks  did  not  appear  until  this  chapter  had 
been  written  up  to  this  point. 


200  THE  PRACTICAL  PHYSICS  OF 

Now,  in  fluids  F  ocpV2  where  p  is  the  density,  and  hence  in 
gases  H  is  proportional  to  V. 

The  weakness  of  this  expression  of  the  theory,  Professor 
Perry  remarked,  lies  in  the  use  of  average  V  and  T,  but  there 
can  be  no  question  as  to  its  importance. 

Professor  Perry  also  remarked  that,  at  present,  the  metal  resist- 
ance was  r-J-u-th  or  TTTV Oth  of  the  whole  heat  resistance,  but  he 
thought  it  possible  to  get  nearly  to  the  condition  in  which  the 
metal  resistance  would  be  the  most  important  heat  resistance. 
In  that  case  it  is  apparent  that  the  phenomena  of  heat  trans- 
mission would  be  strictly  comparable  with  those  of  electrical 
transmission. 

Professor  R.H.  Smith's  Formula. — Of  the  various  formulae  pro- 
posed in  connection  with  this  subject,  that  of  Professor  R.  H. 
Smith1  sought  to  express  the  relation  between  heating  surface, 
boiler  power,  and  boiler  efficiency.  The  following  is  an  out- 
line of  his  examination  of  the  subject  and  of  some  of  his 
terms  : — 

B. H.H. P.  =  Boiler  heat  H. P. = Thermal  units  per  hour  delivered 
to  the  water  x  772-^-1,980,000  (i.e.,  60  x  33,ooo=the  num- 
ber of  foot  pounds  per  hour  required  to  supply  energy  at 
the  rate  of  i  H.P.)=  the  heat  H.P.  of  the  boiler. 
The  latent   heat   of  evaporation    of    i   Ib.    steam   from  and  at 

212°  F.  =  900  ;  then  i  B.H.H.P.=  I>98o>QQO=  2-65  Ibs.  of 

966  x  772 

steam  evaporated  from  and  at  212°  F. — i.e.,  the  evapo- 
rative power  as  usually  stated  -H  2*65,  gives  the  strictly 
definite  measure  of  the  steaming  power  of  the  boiler  in 
H.P.  units.  The  average  of  fairly  good  boilers  and 
engines  gives  i  B.H.H.P.  =  io  I. H.P. 

At  the  rate  of  15  Ibs.  water  per  I. H.P.  per  hour  we  should  have 
5-66  B.H.H.P.  per  I.H.P. 

At  the  rate  of  30  Ibs.  water  per  I.H.P.  per  hour  we  should  have 
'11-32  B.H.H.P.per  I.H.P. 

At  the  rate  of  45  Ibs.  water  per  I.H.P.  per  hour  we  should  have 
16-98  B.H.H.P.  per  I.H.P. 

At  the  rate  of  60  Ibs.  water  per  I.H.P.  per  hour  we  should  have 
22-64  B.H.H.P.  per  I.H.P. 

1  See  "  Industries,"  Vol.  iii.  (1887),  pp.  i,  27,  413. 


THE  MODERN  STEAM  BOILER.  26! 

B.M.H.P.  =  Boiler  mechanical  H.P.  =  the  actual  amount  of 
mechanical  work  done  in  foot  Ibs.  per  hour  by  the  water 
as  it  evaporates  and  expands  into  steam  -i-  1,980,000.  If 
V  cubic  feet  of  steam  be  evaporated  per  hour  at  absolute 
steam  pressure  =  P  Ibs.  per  square  foot,  then 

B.M.H.P.  =_  fV 

1,980,000 

Ratio  of  the  B.H.H.P.  to  B.M.H.P.  for  different  steam 
pressures  : — 

Absolute  steam  pressure  B.H.H.P. 

in  Ibs.  per  sq.  inch.  B.M.H.P. 

10  ...  ...  ...  ...  15-8 

25  ...  ...  ...  ...  I5T 

50  ...  ...  ...  ...  14-6 

75  ...  H-35 

100  14-15 

125  14-05 

150  ...     ...     ...     13-95 

175     ...     i3-85 

200     ...      ...      ...      ...      !3'8o 

225     I3-75 

250     ...     ...     ...     ...     13-70 

XOTK.  The  ratio  is  less  for  high  than  for  lo\v  pressures,  but  the  whole 
variation  is  very  small,  being  15  for  about  15  Ibs.  above  atmosphere,  and  more 
than  13-6  for  300  Ibs.  above  atmosphere,  no  account  being  taken  of  the  effect 
of  priming,  which  would  increase  the  ratio. 

The  B.H.H.P.  depends,  first,  on  the  amount  of  heat  generated 
per  hour  by  the  combustion  of  the  fuel  ;  and,  secondly,  on  the 
proportion  of  that  heat  extracted  from  the  furnace  gases  and 
transmitted  to  the  water.  The  heat  obtained  from  combustion 
depends  necessarily  on  the  quality  of  the  fuel  and  on  the  com- 
pleteness of  the  combustion  ;  and  Professor  Smith  took  as  an 
average  value  14,000  heat,  units  or  10,810,000  foot  Ibs.  per  Ib.  of 
fuel  ;  11,000,000  foot  Ibs.  or  14,250  heat  units  being  taken 
as  a  maximum  for  high-class  coal  and  10,000,000  foot  Ibs.  or 
12,950  heat  units  as  a  minimum  for  poor  fuel. 

Measuring  the  rate  of  heat  generation  in  horse-power  and 
calling  it  furnace  horse-power,  or  F.H.P.,  it  appeared  that  every 

F.H.P.  required     A98o>QOQ     =  -183  Ib.  of  fuel  per  hour. 
14,000  x  772 


202  THE  PRACTICAL  PHYSICS  OF 

The  proportion  of  the  heat  so  generated  that  is  transmitted  to 

T)     T  T     T  T     T) 

the  water,  or  the  ratio     '     '     '   :,  expresses  the  boiler  efficiency 
r  ,ri.t . 

in  view  of  the  heat  utilisation.  Professor  Smith  admits  that  the 
efficiency  so  expressed  ranges  from  50  per  cent,  to  a  little  over 
90  per  cent.,  and  that  it  increases  with  the  length  of  heating 
surface  over  which  the  hot  gases  have  to  travel  before  escaping 
to  the  chimney.  It  is,  of  course,  affected  by  losses  from 
radiation,  conduction,  etc. ;  but,  according  to  Professor  Smith,  it  is 
.increased  by  every  effective  means  taken  to  mix  the  various 
currents  of  gases  thoroughly  together,  so  that  the  hot  currents 
may  be  brought  into  close  proximity  to  the  plates  and  the  colder 
currents  withdrawn  quickly  into  the  parts  of  the  flues  more 
remote  from  the  heating  surface. 

In  calculating  the  rate  at  which  the  gases  cool,  by  giving  up 
their  heat  in  passing  from  furnace  to  chimney,  Professor  Smith 
remarks,  "  We  must  do  so  from  the  average  temperature  over 
the  whole  flue  section.  We  equate  this  to  the  rate  of  conduc- 
tion through  the  plates,  using  a  coefficient  of  conductivity  q  per 
square  foot  per  hour  ;  and  whether  we  use  Peclet's,  Rankine's, 
or  any  other  formula  for  q,  that  value  refers  to  a  surface  differ- 
ence of  temperature  between  gas  on  the  one  side  and  water  on 
the  other  side  of  the  plates.  We  must,  therefore,  allow  for  the 
difference  between  surface  and  average  gas  temperatures,  by 
taking  a  smaller  q  than  would  correspond  by  the  formula  to  the 
average.  This  lessening  of  the  effective  conductivity  increases 
with  the  difference  between  surface  and  average  temperatures, 
and,  therefore,  increases  with  the  size  of  the  tube,  other  things 
being  equal."  "  Taking  all  these  three  equalising  agencies 
(mechanical  mixture,  radiation,  and  conduction)  as  equally  active 
in  large  and  small  tubes,  it  is  evident  that  the  excess  of  the 
average  over  the  surface  temperature  increases  with  the  size  of 
the  tube.  The  measure  of  the  excess,  other  things  being  con- 
stant, may  fairly  be  taken  as  the  ratio  of  the  volume  of  gas  in  the 
flue  to  its  surface.  This  ratio  equals  the  '  hydraulic  mean  depth  ' 
of  the  flue,  being  one-fourth  the  diameter  for  round  and  one- 
fourth  the  side  for  square  tubes.  On  this  account,  the  boiler 
efficiency  may  fairly  be  considered  as  less  than  that  reckoned  on 
the  supposition  of  uniform  temperature  throughout  each  flue 
section,  by  an  amount,  roughly,  at  least  proportional  to  the 


THE  MODERN  STEAM  BOILER.  203 

reciprocal  of  the  hydraulic  mean  depth  of  the  main  flues."  ! 
"  This  does  not  mean,"  adds  Professor  Smith,  "  that  the  efficiency 
is  inversely  proportional  to  the  hydraulic  mean  depth.  If  e  be 
the  efficiency  calculated  for  uniform  distribution  of  temperature  ; 
d  the  hydraulic  mean  depth  of  the  flue  or  tube ;  and  c  a  constant 
at  present  not  known,  but  which  is  not  so  small  as  to  be  unim- 
portant ;  then  the  true  efficiency  would  be 


In  connection  with  this  subject,  Professor  Smith  points  out  that 
although  the  change  from  large  flue  section  to  small  brings  the 
surface  gas  temperature  more  nearly  to  equality  with  the  average, 
and  thus,  perhaps,  increases  the  boiler  efficiency,  yet  it  intro- 
duces a  large  amount  of  factional  and  viscous  resistance  to  the 
passage  of  the  gases  through  the  flue,  which  resistance  has  to  be 
overcome  either  by  the  chimney  draught  or  by  an  equivalent 
furnace  pressure  supplied  by  a  fan  blast,  and  therefore  it  results 
in  higher  temperature  of  chimney  gases.  In  this  way  "  there  is 
quickly  reached  a  thermodynamic  limit  to  the  increased  economy 
obtained  by  increasing  the  ratio  of  length  to  sectional  perimeter 
of  the  flues." 

By  a  series  of  steps  or  "  rules/'  dealing  with  different 
elements  of  the  subject,  Professor  Smith  arrived  at  the  following 
formula  : — 


>2«/j  (50(1—  e). 

S  being  the  heating  surface  in  square  feet  ; 

p  being  a  factor  to  allow  for  loss  by  radiation  and  conduction 
from  the  outside  shell  of  the  boiler  and  by  incomplete 
combustion  ; 

y  being  a  factor  to  allow  for  loss  by  diminution  of  conductivity  by 
sludge  and  scaling,  and  sooting  of  the  plates  ; 

d  being  the  mean  hydraulic  depth  of  the  flues  in  inches  ; 

n  being  the  ratio  of  actual  air-supply  to  that  chemically  required 
for  complete  combustion  ; 

t  being  the  excess  of  steam  temperature  over  outside  air  tempera- 
ture in  degrees  F.  ; 

1  i.e.  their  capacity  -J-  their  surface. 


204 


THE  PRACTICAL  PHYSICS  OF 


e  being  the  furnace  and  boiler  efficiency,  i.e.,  the  ratio  of  heat 
received  by  water  and  steam  to  the  heat  generated  by  com- 
bustion in  the  furnace. 

The  factor  50  was  chosen  by  reference  to  the  experiments  of 
Peclet  on  conduction  from  hot  gas  to  water  through  an  iron 
plate. 

In  calculating  the  heating  surface  required  per  B.H.H.P., 
Professor  Smith  said  that  "  by  assuming  a  steam  pressure  of  75 
Ibs.  per  square  inch  absolute,  and  certain  efficiencies,  and  certain 
values  of  c  ranging  from  3  to  10,  the  following  Table  of  heating 
surfaces  required  per  B.H.H.P.  has  been  calculated.  It  must  be 
remembered  that,  taken  per  engine  I.H.P.,  the  required  heating 
surface  will  be,  on  the  average,  ten  times  as  much.  Taken  per 
B.M.H.P..  it  is  fifteen  times  as  much  for  very  low-pressure,  and 
fourteen  times  as  much  for  high-pressure  boilers.  Certain 
allowances  have  also  to  be  made  as  explained  below." 

TABLE  XLVII. 

HEATING  SURFACE  IN  SQUARE  FEET  PER  B.H.H.P. 


Boiler  efficiency     B'<?^HpR 

'9 

•8 

7 

•6 

'5 

C=-2+2-8n. 

Heating  surface  square  feet. 

3 

•28 

•113 

•070 

•053 

•042 

4 

•627 

•215 

•133 

•095 

'076 

5 

1-494 

.        362 

•219 

•156 

'1  2O 

6 

Impossible. 

'579 

•328 

•233 

•177 

7 

"883 

'479 

•328 

•253 

8 

.I-3I5 

•655 

'447 

•341 

9 

2'OGO 

•902 

•592 

•448 

10 

3-212 

I'2IO 

•766 

'577 

Coal  per  hour 
per  B.H.H.P.F.=-204 

•23 

•26 

•305 

•37 

In  the  above,  c  =  the  total  specific  heat  per  F.  degree  of  all  the 
gaseous  products  of  combustion  of  one  pound  of  fuel,  including 


THE  MODERN  STEAM  BOILER.  205 

the  unburnt  excess  of  air  and  the  inert  nitrogen  of  the  air. 
The  "  allowances  "  referred  to  are  five  in  number  and  result  in 
causing  a  considerable  increase  in  the  surface  required  from  that 
shown  by  the  plotted  curve  of  these  figures.1 

Although  Professor  Smith  gave  effect  to  some  of  these  in  the 
complete  formula  quoted  above,  it  appeared,  from  a  later  endeavour 
to  apply  the  formula  to  the  results  of  trials  of  a  Thornycroft  water- 
tube  boiler,2  that  the  calculation  based  on  the  hydraulic  mean 
depth  of  flues  did  not  fully  apply  to  this  class  of  boilers,  and 
that  the  various  factors  could  not  fully  represent  the  actual 
state  of  affairs.  Moreover,  Professor  Smith's  calculations  take  no 
account  of  the  intensity  of  the  combustion,  which  must  exert  a 
considerable  effect  on  the  rapidity  of  transmission,  and  the 
"  boiler  efficiency  "  term  is,  as  usual,  an  expression  only  in  view  of 
heat  utilisation  apart  from  comparative  dimensions  of  the  boiler, 
so  that  it  is  not  an  expression  of  heat  efficiency  per  unit  of  heating 
surface.  It  has  also  been  remarked,  as  to  Professor  Smith's 
calculated  results  of  the  Thornycroft  trials,  that  "  the  extent  of 
surface  actually  needed  to  give  the  results  of  the  lowest  power 
trial  was  in  excess  of  that  given  by  the  formula,  when  the 
constants  were  adjusted  to  agree  with  the  highest  power  trial, 
in  the  ratio  of  277  to  ri8,  and  the  intermediate  ones  varied 
proportionately." 3 

Both  Mr.  D.  K.  Clark,4  Mr.  J.  A.  Lungridge,5  and  Mr.  M. 
Longridge 6  have  proposed  formulae  dealing  with  the  proportions 
of  locomotive  boilers  and  their  evaporation,  but  none  of  these 
has  been  found  to  embrace  the  rates  of  heat  transmission 
with  varying  proportions  in  that  type  of  boilers  alone,  and 
it  is  apparent  that  the  wide  differences  in  design  in  water- 
tube  boilers  render  these  formulae  even  more  inapplicable 
to  them. 

Mr.  Hudson's  Formula. — The  only  formula  for  heat  trans- 
mission, including  a  factor  for  velocity  of  the  hot  gases,  which 

1  See  "  Industries,"  Vol.  iii.,  p.  28. 

2  Min.  Proc.  Inst.  C.E.,  Vol.  xcix.,  pp.  135-138,  145. 

3  Mr.  J.  G.  Hudson  in  The  Engineer,  Vol.  Ixx.  (1890),  p.  449. 

4  Min.  Proc.  Inst.  C.E.,  Vol.  xii.,  pp.  382-449. 

5  Min.  Proc.  Inst.  C.E.,  Vol.  Iii.,  pp.  98-176. 

6  Manchester  Association  of  Engineers,  January,  1890  ;  refer  also  to  Prof. 
R.  Werner,  Zeit.  des  Ver.   Dent.  Ingen.  (1883),  pp.  394-398,  abs.  in   Trans. 
N.  of  E.  Inst.  M.  Eng.,  Vol.  33,  p.  77. 


206  THE  PRACTICAL  PHYSICS  OF 

has  been  as  yet  proposed  in  anything  like  a  complete  shape,  is 
given  by  Mr.  J.  G.  Hudson,  in  his  articles  on  "  Heat  Trans- 
mission in  Boilers,"  in  The  Engineer,  Vol.  Ixx.,  pp.  449,  483,  523. 
Mr.  Hudson  reasoned  from  the  results  of  Mr.  C.  Lang's  experi- 
ments (seep.  138  ante)  on  evaporation  with  steam  heat,  and  from 
the  figures  given  by  Mr.  Wm.  Anderson  (in  Min.  Proc.  Inst.  C.E 
1883-84,  "  Heat  Lectures")  as  to  the  probable  temperature  of  the 
plates  of  a  boiler  over  the  furnace. 

To  cause  the  maximum  evaporation  given  in  Mr.  Lang's 
results  the  total  difference  of  temperature  needed  would,  accord- 
ing to  Mr.  Hudson,  be  only  ^ 5  =36*4  degrees.  "  The 

heating  steam  would  therefore  need  a  temperature  of 
340  -f  36  =  376  degrees,  but  the  hotter  side  of  the  heating 
surface  would  be  even  cooler  than  this  by  the  differ- 
ence required  to  cause  the  transfer  of  heat  from  the 
steam  to  the  surface."  "  Now,"  said  Mr.  Hudson,  "  in 
effecting  the  same  rate  of  evaporation  by  fire  heat  instead 
of  steam,  the  same  amount  of  heat  has  to  be  trans- 
mitted, and  there  should  be  no  change  as  regards  the  head  or 
difference  of  temperature  needed  for  the  conduction  of  this  heat 
through  the  thickness  of  the  metal,  nor  for  its  emission  to  the 
water.  The  temperature  of  the  metal  will  therefore  remain 
unaltered."  Here,  however,  Mr.  Hudson  assumes  too  much,  as 
the  experiments  recorded  in  this  chapter  prove.  Even  taking 
Mr.  Anderson's  limit  of  the  melting  point  of  lead  as  showing  the 
temperature  to  which  the  boiler  plates  have  not  been  raised, 
there  might  still  be  a  considerable  rise  in  temperature  above 
376°  F. 

Mr.  Hudson  proceeds  to  say  :-  "  It  is  not  known  what  furnace 
temperature  would  be  'needed  to  effect  the  rate  of  evaporation 
assumed,  but  it  would  undoubtedly  be  high,  probably  not  less 
than  2500°  F.  ;  and  it  seems  difficult  to  escape  the  conclusion 
that  of  the  temperature  difference  of  2500°  —  340°  =  2160°,  no 
less  than  2160°  —  36°  =  2124°  or  98-3  per  cent.,  plus  the  difference 
required  in  the  case  of  steam,  must  be  needed  to  effect  the 
transfer  of  heat  from  the  hot  gases  to  the  metal,  the  remaining 
36°=  i '7  per  cent.,  minus  the  same  quantity,  sufficing  to  carry 
the  heat  through  the  metal  and  into  the  water.  The  only  loop- 
hole for  substantial  error  in  the  above  calculation  would  seem  to 


THE  MODERN  STEAM  BOILER.  207 

be  the  possibility  that  in  a  crowded  boiler  the  movement  of  the 
water  might  be  less  active  than  in  the  steam  evaporator,  causing 
a  larger  difference  to  be  needed. for  the  emission.  An  extreme 
allowance  for  this  would  be  to  halve  the  rate  of  transmission, 
which  would  give  the  metal  a  higher  temperature  by  less  than 
36  degrees." 

Following  this  line  of  argument,  Mr.  Hudson  proceeded  to 
inquire  in  what  relative  proportions  the  total  head  of  tempera- 
ture should  be  allotted  to  the  absorption,  conduction  and  emis- 
sion respectively,  and  proposed  the  following  as  a  rough  approxi- 
mation :  "  In  the  first  place,  some  idea  of  the  head  needed  to 
overcome  the  internal  resistance  of  the  metal  can  be  obtained 
for  temperatures  not  exceeding  500°  or  600°  F.  from  the  follow- 
ing formula,  based,  for  wrought  iron,  on  Forbes'  experiments 
on  the  conducting  powers  of  that  metal,  between  32°  and  527°, 
and  for  other  metals  on  Dispretz's  data  as  to  their  relative  con- 
ducting powers. 

Q  =  Units  transmitted  per  square  foot  per  hour. 

R  =  Rate  of  transmission  for  lin.  thickness,  i  square  foot,  I 
hour,  and  i  cleg.  Fah.  at  32  deg.  =  for  copper  1243  units,  brass 
1044,  cast  n"on  783,  wrought  iron  or  steel  522. 

D  =  Difference  in  degs.  Fah.  required  to  overcome  the  internal 
resistance. 

/  =  Thickness  of  the  metal  in  inches. 

T  =  Mean  temperature  of  the  metal. 

Then— 

Q  _  D  x  R  x  (1467-5  -  T) 

t  x  J435'5 

and — 

D  =     Q  x  *  x  *435'5 
"  R  x  (1467-5  -  T) 

"  For  copper  tubes  of  10  B.W.G.  thickness  (as  used  in  Mr. 
Lang's  experiments)  at  the  assumed  duty,  this  formula  gives 
6  deg.  as  the  head  needed  for  the  conduction  alone.  How  the 
balance  of  30  cleg.,  available  in  the  case  of  steam  as  the  heating 
agent  for  the  surface  absorption  and  emission,  should  be  appor- 
tioned, is  of  little  moment  for  the  present  purpose.  No  doubt 
the  steam  side  would  need  less  than  the  water,  and  taking  the 
ratio  of  i  to  2,  giving  10  deg.  and  20  deg.  respectively,  the 
various  temperatures  would  stand  as  follows  : 


2o8  THE  PRACTICAL  PHYSICS  OF 

Steam.  Fire. 

Heating  medium             ...         376°  2500° 

Difference  for  absorption  10°                       2I34° 

Surface,  hotter  side         ...         366°  366° 

Difference  for  conduction  6°                             6° 

Surface,  next  water         . . .         360°  360° 

Difference  for  emission  20°                           20° 

Water  in  boiler  ...         ...         340°  340 


.0 


Total  difference         ...          36°  2160° 

"  For  an  iron  or  steel  plate  J  in.  thick,  the  difference  would  be 
55  deg.  instead  of  6  deg.,  requiring  an  important  addition  to  the 
temperature,  or  involving  a  considerable  reduction  in  the  duty  in 
the  case  of  the  steam,  but  only  an  unimportant  variation  in  either 
respect  for  the  fire.  For  lower  rates  of  evaporation  than  that 
assumed,  the  differences  wrould  be  divided  out  in  very  much  the 
same  way,  except  that  the  head  needed  for  conduction  would 
be  even  less  in  proportion." 

Consistently  with  this  reasoning  Mr.  Hudson  concluded  that 
"  in  evaporating  by  fire  heat,  the  whole  of  the  difference  may, 
for  all  practical  purposes,  be  taken  as  available  for  effecting 
the  transfer  of  heat  from  the  gases  to  the  metal,  and  the 
latter  may  be  considered  as  having  the  same  temperature 
as  the  water."  Also  that,  "  however  valuable  an  active 
circulation  in  a  boiler  may  be,  on  other  grounds,  no  activity 
beyond  that  needed  for  keeping  water  in  contact  with  the 
heating  surfaces  can,  by  reducing  the  difference  needed 
for  emission,  appreciably  increase  the  quantity  of  heat  trans- 
mitted, seeing  that  the  amount  of  the  difference  capable  of 
being  influenced  in  this  way  is  such  a  trifling  fraction  of  the 
whole." 

It  cannot  be  maintained,  however,  that  either  of  these  conclu- 
sions is  firmly  established.  Later  experiments  have  shown  that 
the  metal  has  not  the  same  temperature  as  the  water,  but,  on  the 
contrary,  that  the  temperature  of  the  fire  surface  of  the  plates 
bears  a  well-defined  relation  to  the  flow  of  heat  through  the 
metal  and  to  the  thickness  of  the  metal  when  the  rate  of  flow  is 
constant.  It  has  also  been  found  that  the  velocity  of  movement 
of  the  water  has  a  decided  influence  upon  the  rate  of  flow  of 


THE  MODERN  STEAM  BOILER.  209 

heat,  and  this,  apart  from  questions  as  to  the  temperature  of  the 
plate,  or  the  so-called  emission  or  emissive  power  of  the  surface. 
The  second  of  Mr.  Hudson's  conclusions  is,  in  fact,  at  variance 
with  his  own  subsequent  remarks  on  the  effect  of  velocity  of 
movement,  although  in  them  he  is  mainly  occupied  with  the 
movement  of  the  gases.  Still,  he  says,  "  in  the  case  of  heating 
water  by  steam,  it  can  be  conclusively  shown  that,  other  things 
being  equal,  the  quantity  of  heat  taken  up  by  the  water  is  almost 
wholly  a  question  of  the  speed  with  which  the  latter  traverses 
the  heating  surface,  the  transmission  increasing  only  somewhat 
less  rapidly  than  the  speed.  So  important  is  this  influence,  that 
the  transmission  has  been  found  to  vary  from  as  little  as  20  or 
30  units  per  degree,  where  the  water  was  confined  in  small  tubes 
and  moved  very  slowly,  up  to  nearly  1,000  units  according  to  the 
speed."  "  Knowing  this,"  Mr.  Hudson  proceeds,  "  it  is  natural 
to  ask  whether  the  speed  of  the  gases  in  a  boiler  might  not  in 
like  manner  affect  the  activity  of  the  transmission,  and,  the  idea 
once  started,  much  confirmatory  evidence  suggests  itself,  and  the 
theory  seems  to  account  for  much  previously  unexplained."  It 
will  be  observed  that  Mr.  Hudson  speaks  of  heating  water  by 
steam,  but  it  stands  to  reason  that  if  movement  of  the  water  has 
been  found  to  accelerate  heat  transmission  with  the  moderate 
difference  of  temperature  which  that  system  of  heating  provides, 
it  must  be  all  the  more  necessary  in  presence  of  the  much  higher 
temperatures  provided  by  fire  gases.  With  regard  to  the  neces- 
sity for  rapid  movement  of  the  gases  Mr.  Hudson  is  clear  and 
emphatic  in  the  arguments  which  he  advances  in  support  of  it, 
but  is  mistaken  in  the  idea  that  the  element  of  speed  had  not 
been  previously  taken  into  account  as  possibly  affecting  the 
transmission.  Peclet,  Craddock,  Osborne  Reynolds,  Hagemann, 
and  Louis  Ser,  at  least,  had  previously  shown  the  necessity  for  it 
and  some  of  its  effects  experimentally.  Nevertheless,  among 
engineers,  Mr.  Hudson  led  the  way  in  appreciation  of  its  influ- 
ence. "That  the  speed  might,  not  unreasonably,  be  expected 
to  affect  the  result  in  one  direction  or  the  other,  it  is  natural  to 
suppose,"  he  remarked,  "  when  the  extent  of  its  variation  is 
apprehended.  In  a  lightly  fired.  Lancashire  boiler  it  may  be 
under  4  ft.  per  second,  range  from  that  speed  up  to  140  ft.  in  a 
locomotive,  and  reach  considerably  over  200  ft.  in  a  loco,  type 
torpedo  boiler  when  hard  pressed.  The  influence  of  the  speed 


210  THE  PRACTICAL  PHYSICS  OF 

seems  to  explain  the  following  anomalies  :  (i)  The  injury  to  a 
boiler  from  the  use  of  forced  draught  is  almost  invariably  con- 
fined to  overheating  the  tubes,  though  the  lire-box  plate  surfaces 
are  exposed  to  an  even  higher  temperature.      (2)  The  generally 
inferior    efficiency  of    water-tube,  as   compared  with    lire-tube 
boilers.     (3)  The  high  efficiency  of  locomotive  boilers,  consider- 
ing their  small  extent  of  surface  in  proportion  to  fuel  burnt. 
(4)    The    comparatively    high    efficiency    of   boilers   worked   at 
extreme  rates ;  thus  the  locomotive  type  torpedo  boiler  tested  at 
Portsmouth  had,  in  the  highest  duty  trial  with   6   in.  draught, 
only  the  very  small  proportion  of  -34  sq.  ft.  of  surface  per  i  Ib. 
of  fuel.     The  reduction  of  the  gases  w?ith  this  small  surface   to 
1444°  corresponds  with  a  transmission  per  degree  several  times 
greater  than  is  attained  by  boilers  working  at  more  ordinary 
rates.     (5)  The  slight  increase  in   economy  to   be  obtained  by 
reducing  the  weight  of  fuel  burnt  in  a  given  boiler  below   a 
certain  point,  changing  at   last   to    an    actual   falling   off.     An 
extreme  example  of  this  is  found  in  the  trials  of  a  sectional  boiler 
for  the  Kimberley  Water  Works,  in  which  the  evaporation  from 
and  at  212°  was  10*87  Ibs.  w^n  3'^4  sq.  ft.  heating  surface  per 
i  Ib.  fuel,  reached  11-5  Ibs.  with  6-44  sq.  ft.,  and  fell  to  8*15  Ibs. 
at  the  extreme  proportion  of  i6'i  sq.  ft.     (6)  The  circumstance, 
of  which  many  examples  might  be  quoted,  that  the  mischievous 
effect  of  an  excessive  supply  of  air  is  usually  limited  to  the  carry- 
ing to  waste  of  little   more  than  the  extra  heat  corresponding 
with   the   extra  weight  of  the   gases,   their  temperature  being 
nearly  the  same  for  all  ordinary  quantities  ;  though  if  the  trans- 
mission were  proportional  to  the  temperature  merely,  that  of  the 
waste  gases  wroulcl  be  considerably  higher  with  the  larger  supply. 
An    excessive   air  supply  does  not,  as    might  at  first  sight  be 
expected,  result  in  a  low  temperature  of  the  waste  gases,  unless 
the  proportion  of  heating  surface  to  fuel  is  so  limited  that  the 
smaller  volume  of  gases,  originally  hotter  because  of  its  smaller 
heat  capacity,  but  therefore  also  more  rapidly  cooled,  has  not 
time  to  fall  to  the  temperature  of  the  larger,  originally  cooler, 
but  more  slowly  cooling  volume.     The  larger  volume  will,  how- 
ever, be  found  to  transmit  more  heat  per  degree   of  difference, 
;  though  it  loses  temperature  more  slowly,  owing  to  its  greater  heat 
capacity,  and  it  would  appear  that  this  greater  transmission  is 
due  to  the  greater  speed." 


THE  MODERN  STEAM  BOILER.  211 

Mr.  Hudson  proposed  the  following  formulae  and  coefficients 
as  embodying  his  conclusions  on  the  whole  subject.  He  said, 
"  They  are,  of  course,  applicable  only  to  surfaces  in  constant 
contact  with  water.  For  simplicity's  sake,  the  transmission  from 
the  gases  has  been  calculated  step  by  step,  for  increasing 
intervals,  as  a  formula  representing  the  continuous  action — if 
such  could  be  framed — would  unavoidably  be  too  complex  for 
convenient  use."  "  The  formula  for  fire-box  transmission  is 
unavoidably  empirical  and  without  a  rational  basis,  as  the  trans- 
mission here  could  not  be  calculated  on  the  difference  of 
temperature  as  for  the  tubes,  because  in  a  fire-box  the  tempera- 
ture of  the  gases  is  neither  uniform  nor  the  same  as  that  of  the 
fuel." 

Hd  =  Heat  units  developed  per  i  Ib.  fuel,  less  latent  heat  of 

any  moisture  evaporated  from  the  fuel. 
H(,  =  Heat    units    available    above    temperature    of     steam, 

=  H.— w  (T— 60). 

A     =  Ibs  air  per  Ib.  fuel  ;  assumed  temperature  60°  F. 
s      =  specific  heat  of  gases,  taken  as  -24. 
iv    =  heat  capacity  of  gases,  =  s  (A  +  i). 
F     =  heating  surface   exposed  to  radiant  heat  from  fuel  or 

flame,  in  square  feet  per  Ib.  fuel. 
S     =  tube  or  flue  surface,  square  feet  per  Ib.  fuel. 
v      =  speed  of  gases  in  tubes  or  flues,  feet  per  second. 
Tg   =  temperature  of  gases,  degrees  Faht. 
Ts   =  temperature  of  steam,  degrees  Faht. 
B     =  coefficient    of     transmission,    =    1250    when    same  is 
calculated   step   by  step  for  successive  intervals,  ter- 
minating  at  the  following  values  of  S,  respectively  : 
•°5»  *i5i  '3»  '5,  '8,  1-3,  2,  3,  4-5,  6-5,  9. 
Then,  heat-units  absorbed  in  fire-box  per  i  Ib.  fuel. 

A        \ 


=  Hrt  x      i  -—      —  J       .     .     .     .     (i) 
\         A  4-  4S  F/ 

Available  heat-units  remaining  in  gases  leaving  fire-box 


Temperature  of  gases  leaving  fire-box 


212  THE  PRACTICAL  PHYSICS  OF 


Speed  of  gases    =  v  =  A  x  (T,  +  .  (4) 

144,000  C 

Units  transmitted  per  square  foot  per  degree  per  hour  in 
tubes  or  flues 

_  T,  +  T5  +  922       vV 
~^~  ~B 

Some  tables  of  results  obtained  by  the  use  of  these  formulas, 
and  some  diagrams  of  curves  will  be  found  in  Chap.  IX. 

It  will  be  interesting  to  compare  with  Mr.  Hudson's  estimates 
the  following  figures  of  the  actual  velocity  of  gases  in  boiler 
flues  as  given  by  Mr.  J.  T.  Milton1:  "  Taking  an  ordinary 
return-tube  boiler,  burning  17  Ibs.  of  coal  per  square  foot  of 
grate,  and  using  24  Ibs.  of  air  per  pound  of  fuel,  and  assuming 
a  temperature  of  1664°  and  887°  at  the  ends  of  the  tubes, 
temperatures  given  by  Mr.  Oram  as  having  been  verified  in  some 
experiments  made  at  Devonport  with  this  class  of  boiler,  it  will 
be  found  that  the  gases  have  a  velocity  of  about  32  feet  per 
second  on  entering  the  tubes,  and  of  20  feet  per  second  on 
leaving  them  ;  their  mean  velocity  will  therefore  be  about 
26  feet  per  second,  and  the  time  taken  to  traverse  a  tube 
6  ft.  6  ins.  long  will  be  only  J  second.  The  total  time  any 
portion  of  gas  remains  in  the  boiler  is  thus  probably  consider- 
ably less  than  a  second.  In  a  Belleville  boiler  of  the  type  used 
in  the  '  Powerful,'  assuming  a  consumption  of  24  Ibs.  per 
square  foot  of  grate,  Mr.  Oram  gives  the  funnel  temperature 
as  650°.  Assuming  the  same  proportion  of  air  as  before,  and 
that  the  temperature  of  gases  when  entering  the  tubes  is  1600°) 
the  velocity  at  the  entrance  between  the  tubes  will  be  about 
32  feet,  and  at  exit  17  feet  per  second  ;  the  time  taken  in 
traversing  the  tube  spaces  will  be  about  j-  second,  and  the 
total  time  in  the  boiler  will  be  about  £  second,  which  is  not 
very  different  to  the  time  the  gases  remain  in  the  ordinary 
boiler." 

With  forced  combustion  and  high  rates  of  combustion  these 
times  are  proportionately  reduced. 

Professor  Rankings  Formula.  —  In  connection  with  this  subject 
reference  is  constantly  made  to  Professor  Rankine's  formula  (on 

1  Min.  Proc.  Inst.  C.E.  VoKcxxxvii,  p.  173.  See  also  Chap.  III.  p.  66  (ante) 
velocity  of  gases. 


THE  MODERN  STEAM  BOILER.  213 

p.  260  of  "  A  Manual  of  the  Steam  Engine,"  etc.,  1859)  as  if  it 
were  a  final  and  ultimate  expression  of  law  on  this  subject. 
Nothing  could  be  more  mistaken  than  this  idea. 

Professor  Rankine  stated  (at  p.  257)  that  the  rate  of  internal 
conduction  through  a  given  substance,  expressed  in  thermal 
units  per  square  foot  of  area  per  hour,  is  proportional 

1.  To  the  rate  at  which  the  temperature  varies  along  a  line 

perpendicular  to  the  section  through  which  the  heat  is 
passing,  and 

2.  To    the    internal    conductivity    of    the    substance,    which 
depends  upon  its  nature. 

When  heat  is  passed  across  a  metal  plate  from  a  fluid  on  one 
side  to  another  at  the  opposite  side,  factors  of  external  and 
internal  thermal  resistance  are  introduced,  and  when  the  total 
thermal  resistance  is  thus  provided  for,  Professor  Rankine  thus 
expressed  the  rate  of  conduction— 

T'-T 

or    -\-a-\-pX 

"  when  T'  and  T  are  now  the  temperatures  not  of  the  two 
surfaces  of  the  plate,  but  of  the  two  fluids  which  are  respectively 
in  contact  with  its  two  faces  "  ; 

<r'  +  tr  being  the  coefficients  of  external  resistance,  and 
P  being    the    coefficient    of    internal    resistance    (estimated    by 
Rankine  at  '0096^,  when  q  is  expressed  in  thermal  units  per 
hour  per  square  foot  of  area  and  x  in  inches), 
x  being  the  thickness  of  the  plate. 

After  giving  from  Peclet  an  expression  for  the  value  of  &' 
+  <r,  Professor  Rankine  proceeded  to  introduce  his  empirical 
formula  as  follows  : — 

"  It  will  be  shown  in  a  subsequent  article  that  the  results  of 
experiments  on  the  evaporative  power  of  boilers  agree  very  well 
with  the  following  approximate  formula  for  the  thermal  resist- 
ance of  boiler  plates  and  tubes — 

n 


T'-T 

which  gives  for  the  rate  of  conduction  per  square  foot  of  surface 
per  hour — 


2I4 


THE  PRACTICAL  PHYSICS  OF 


He  added,  "  This  formula  is  not  proposed  as  being  more  than 
a  rough  approximation,  but  its  simplicity  makes  it  very  con- 
venient, and  it  will  be  shown  that  it  is  near  enough  to  the  truth 
for  its  purpose.  The  value  of  a  lies  between  160  and  200." 
The  results  of  experiments  referred  to  in  this  extract  are  given 
on  pages  295  to  298  of  "  The  Steam  Engine  "  (same  edition), 
and  they  are  of  far  too  crude  a  nature  to  serve  as  the  foundation 
of  anything  but  "  a  rough  approximation." 

The  following  remarks  by  Professor  R.  H.  Smith  show  also 
the  wide  divergence  between  Rankine's  empirical  formula  and 
Peclet's  rule  : — 

"  From  Peclet's  experiments,  the  rate  of  conduction  in 
English  heat  units  per  hour  per  square  foot  may  be  called  q, 
"and  appears  to  be 

g  =  i78{i  +  -0037   (/-/>)}(/  -tb) 

where  /  is  the  surface  gas  temperature,  and  tb  that  of  the  water 
in  the  boiler.  A  few  examples  of  the  results  of  this  formula  are 
given  in  the  annexed  Table — 


TABLE  XLVIII. 


/   ft 

« 

(t—  tb)* 

120 

IOO 

244 

83 

2OO 

620 

333 

50O 

2,540 

2,083 

1,000 

8,380 

8,333 

1,500 

17,520 

i8,75o 

2,OOO 

29,960 

33,333 

"  The  third  column  gives,  for  the  sake  of  comparison,  the 
results  of  a  formula  of  the  form  suggested  and  used  by  Rankine. 
Rankine,  however,  gives  the  divisor  to  be  used  in  this  latter  as 
lying  between  160  and  200.  With  this  it  would  never  agree 
with  Peclet's  results,  except  for  such  high  temperatures  as  do 
not  occur  in  boilers,  even  in  the  fire-boxes.  With  the  divisor 
120  it  is  seen  to  agree  for  a  temperature  difference  of  about 


THE  MODERN  STEAM  BOILER.  215 

1000°,  to  give  too  small  figures  for  low  temperatures,  and 
about  10  per  cent,  too  high  for  about  2000°  temperature 
difference." 

Professor  Witz's  Experiments. — It  remains  for  us  to  notice  some 
experiments  carried  out  by  Professor  Aimee  Witz  (and  recorded 
in  the  "  Comptes  Rendus  de  1' Academic  des  Sciences,"  Paris, 
Vol.  cxiv.,  1892,  p.  41 11))  on  account  of  the  light  which  they 
throw  upon  the  effect  of  increasing  the  temperature  of  the  metal 
plates  in  contact  with  water,  and  also  because  of  the  remarkable 
rate  of  evaporation  reached  in  one  or  two  instances.  The  first 
series  of  experiments  showed  the  time  required  to  evaporate 
40  grammes  (1-41  oz.)  of  water  at  different  temperatures  of 
plate — 

TABLE  XLIX. 

Time  required. 
At  141°  Cent,  or  286°  Fahr....          ...          ...     2  min.    o  sec. 

M   T94     j,        ,.    38i     „       ...  ...     o     „     38    „ 

»  243     i,        »   47°     »       ••«  •••     °     »     25    „ 

„     260       „  „     500       „  O       „        22 

„     320       „  „    608       „  O       „        20 

„  cherry  red...          ...          ...   10     ,,     20 

In  the  last  instance  the  spheroidal  condition  of  the  water  was 
realised,  and  the  rate  of  evaporation  became  at  once  31  times 
less  than  that  at  320°  C.  In  order  to  prove  whether  the 
spheroidal  condition  was  likely  to  be  realised  easily  with  a 
larger  quantity  of  water  in  a  boiler,  a  series  of  experiments  was 
then  made  with  a  small  vertical  cylindrical  boiler  3*017  deci- 
metres (practically  12  inches)  diameter,  so  constructed  that 
various  thicknesses  of  bottom  plate  from  i  to  12  millimetres 
could  be  used.  The  water  was  maintained  at  a  constant  level, 
the  quantity  evaporated  in  given  time  being  measured,  but  the 
temperature  of  the  plate  was  not  measured,  as  the  result  inquired 
into  was  that  of  the  possible  rate  of  evaporation  with  excessive 
heating,  and  the  possibility  of  the  spheroidal  condition  occurring. 
The  following  Table  gives  results  with  a  height  of  3*15  inches  of 
water. 

1  For  abstract  see  Min.  Proc.  Inst.  C.E.     Vol.  cviii.,  p.  473. 


THE  PRACTICAL  PHYSICS  OF 


TABLE  L. 


Nature  of  Heating. 

Barometric 
Pressure. 

Temperature  of  Feed 
Water. 

Water  evaporated 
per  hour. 

Centigrade 

degrees. 

Faht. 
degrees. 

Kilog.  per 
Sq.  Metre. 

Lbs.  per 
sq.  foot. 

Seven  Bunsen  Burners  ... 

29*33 

15 

59, 

63-3 

I3-0 

Seven     Bunsen     Burners 

and  one  air  blast 

29-84 

16 

61 

1  79'  4 

36-8 

Seven     Bunsen    Burners 

and  one  oxy-hydrogen 
blow  pipe 

29-84 

18 

65 

200-9 

41-2 

Seven    Bunsen     Burners 

and  three  blow  pipes... 

29-65 

T9 

67 

263-2 

54'° 

Coke  with  air  blast 

29-92 

19 

67 

433-5 

88-9 

Seven    Bunsen    Burners, 

one   air  blast,  and  one 

oxy-h  ydrogen  blow 
Pipe       

29-70 

14 

57 

662-8 

136 

Coke  with  air  blast 

29-92 

90 

194 

994'3 

204 

In  the  case  of  the  last  two  experiments  the  water  was  first  all 
evaporated  away,  and  the  plate,  which  \vas  12  millimetres,  or 
practically  \  inch  thick,  was  allowed  to  become  red  hot,  when 
the  feed  water  was  again  admitted,  and  the  level  maintained  as 
before.  In  none  of  the  first  live  experiments  did  the  plate 
become  red  hot,  the  surface  of  the  plate  in  contact  with  the 
water  having  been  carefully  cleansed.  The  supports  of  the 
boiler  were,  however,  raised  to  a  dark  red  heat,  and  the  water 
was  violently  agitated.  In  the  last  two  cases  the  plate  remained 
red  hot,  without  perceptible  cooling  in  the  last  case,  and  the 
boiling  was  very  violent.  Although  Professor  Witz  concluded 
that  the  water  in  a  boiler  need  not  necessarily  assume  the 
spheroidal  state,  even  if  the  plates  became  red  hot,  yet  the 
danger  of  explosion  would  be  none  the  less  present,  on  account 
of  the  inability  of  the  metal  to  resist  the  strain  of  steam  pressure 
at  that  temperature. 

The  second  last  result  shows  a  similar  rate  of  evaporation  to 
that  which  was  attained  in  Mr.  C.  R.  Lang's  experiments,  and 
we  are  thus  shown  that  a  definite  rate  of  heat  transmission  may 
take  place  with  widely  different  static  conditions  of  temperature 
in  the  metal  plate. 


THE  MODERN  STEAM  BOILER.  217 

It  is  to  be  regretted  that  more  extended  information  regarding 
these  experiments  of  Professor  Witz  was  not  published,  as  much 
might  be  learned  from  them  if  all  the  conditions  were  made 
known.  We  may,  however,  conclude,  from  all  the  evidence 
which  has  been  before  us,  that  each  square  foot  of  heating 
surface  in  a  boiler  properly  constructed  and  worked  should  be 
good  for  the  evaporation  of  from  80  to  100  Ibs.  of  water, 
per  hour.  Theoretically,  considering  the  question  of  conduction 
through  the  metal  alone,  the  heat  requisite  for  a  much  larger 
result  should  be  readily  transmitted,  but  making  allowance  for 
resistance,  and  presuming  that  Professor  Perry's  hopeful  antici- 
pation (noted  on  p.  200,  ante)  is  not  at  once  realised,  an  increase 
from  the  presently  accepted  10  Ibs.  per  square  foot  per  hour  to 
anything  approaching  the  figures  given  above,  is  very  much 
wanted. 

Reference  may  also  be  made  to  the  Paper  on  the  Efficiency 
of  Steam  Boilers  and  Surface  Condensers  read  by  T.  E.  Stanton 
to  the  Owens  College  Engineering  Society,  and  published  in  the 
Mechanical  Engineer,  31  March,  1900,  Vol.  v.,  pp.  445-448  ; 
and  to  the  Theoretical  Consideration  of  Evaporation  in  Boilers 
by  H.  Brillie,  in  Le  Genie  Civil,  August  and  September,  1897, 
pp.  260  et  scq.  (see  Abs.  in  Min.  Proc.  Inst.  C.  E.,  Vol.  cxxxi., 
p.  480.) 


CHAPTER    V. 

CIRCULATION  OF  WATER. 

IT  is  in  connection  with  the  transmission  of  the  heat  in  boilers 
that  the  circulation  of  the  water  possesses  its  chief  importance. 
Were  water  a  good  conductor  of  heat,  like  mercury,  motion 
would  not  be  to  the  same  extent  necessary,  even  though  the  heat 
vibrations  had  to  adapt  themselves  to  a  liquid  form  of  matter  in 
passing  to  it  from  a  solid.  Freedom  of  escape  for  the  vapour 
from  the  liquid  would  be  the  principal  condition  needing  a 
proper  provision,  and  under  such  circumstances  the  greatest 
heat  would  be  applied  to  the  liquid  near  the  surface,  and  a  less 
temperature  as  the  distance  from  that  part  increased.  Water 
being  a  bad  conductor  of  heat,  it  is  only  by  means  of  convection 
currents  that  the  total  quantity  of  water  contained  in  a  boiler 
can  readily  be  heated  up  to  and  maintained  at  or  near  the  tem- 
perature of  steam  formation.  The  direction  of  movement  of 
these  convection  currents  is  an  upward  one,  in  accordance  with 
the  laws  of  gravity,  the  heated  portions  of  water  being  rendered 
specifically  lighter  by  their  expansion.  Hence  in  most  boilers  the 
fire  is  placed,  or  the  heat  of  the  fire  is  applied,  at  as  low  a  point 
as  possible,  and  no  attempt  is  made  to  heat  the  water  from  above 
downwards.  In  this  way  the  movement  of  the  heated  particles 
of  water  assists,  and  in  turn  is  assisted  by,  that  of  the  steam,  and 
when  the  tubes  or  water  passages  are  of  small  area  individually, 
in  result  the  water  is  carried  along  at  a  considerable  speed. 
Water-tube  boilers,  in  general,  present  conditions  which  produce 
a  rapidity  of  such  movement  of  the  water  much  beyond  what 
could  be  known  in  tank  or  drum  boilers,  and  it  is  no  doubt  in 
great  part  to  this  that  their  comparatively  rapid  steaming  power 
is  due.  Yet  further  examination  shows  that  movement  of  that 
kind  is  perhaps  _not  an  unmixed  blessing,  because  large  quantities 
of  water  which  cannot  be  at  the  full  temperature  of  the  steam 
are  carried  along  with  the  currents  and  thrown  forcibly  into  the 
steam  space  in  the  closest  contact  with  the  steam.  Before  they 
can  be  separated  from  the  steam  and  returned  to  the  water  space 

218 


THE  MODERN  STEAM  BOILER.  219 

by  down-comers,  there  is  no  doubt  that  they  must  exert  a  sensible 
cooling  effect  on  the  steam,  and  probably  they  thus  cause  the 
work  of  steam  formation  to  some  extent  to  be  done  over  again 
by  a  further  expenditure  of  heat.  Certainly  if  the  steam  could 
at  once  escape  from  the  hottest  portion  of  the  water  into  the 
steam  space  without  the  necessity  for  its  mingling  with  any 
water  of  a  less  temperature,  some  useless  expenditure  of  heat 
would  be  prevented,  and  we  should  be  a  step  nearer  the  realisa- 
tion of  the  best  result.  We  have  seen  in  Chapter  IV.  that  rapid 
movement  of  the  water  is  absolutely  essential  to  heat  transmis- 
sion, and  therefore  the  problem  that  lies  before  us  is  that  of 
how  to  produce  the  maximum  useful  rate  of  movement  of  the 
water  over  the  heating  surface  whilst  the  minimum  quantity  is 
allowed  to  mingle  with  the  steam.  In  any  solution  of  this 
problem  we  have  also  to  provide  for  the  passage  of  the  currents 
of  water  and  hot  gases  in  opposite  directions,  as  it  is  quite  clear 
that  this  arrangement  is  demanded  as  one  of  the  conditions  of 
successful  heat  transmission. 

The  circulation  of  water  in  boilers  has  usually  been  considered, 
mainly,  if  not  wholly,  in  view  of  the  prevention  of  over-heating 
portions  of  the  boiler  surfaces,  and  investigations  of  the  action 
have  hitherto  been  concerned  almost  entirely  with  the  quantity 
of  water  put  in  motion  in  individual  boilers,  and  with  the  mode 
in  which  this  movement  has  been  produced  in  them.  Conse- 
quently in  almost  all  treatises  on  boilers  the  circulation  of  the 
water  has  been  dealt  with  as  if  it  were  a  sort  of  independent 
action  regulating  the  work  done  by,  and  the  life  of,  boilers,  and 
therefore  requiring  provision  for  its  being  unhindered,  but  only 
so  that  rapid  steaming  should  proceed  without  damage  to  the 
boiler,  and  not  in  strict  relation  to  the  requirements  of  heat- 
transmission. 

The  truth,  however,  is,  that  water  circulation  is  one  of  the 
things  connected  with  the  action  of  boilers  which  itself  requires 
to  be  governed  and  directed,  in  order  that  the  highest  degree  of 
efficiency  in  steam  raising  may  be  reached,  and  in  this  view  the 
velocity  of  the  movement  of  the  water  requires  to  be  considered. 

Two  Kinds  of  Circulation. — There  are  evidently  two  kinds  of 
circulation  possible  : — 

i.  That  which  is  due  to  the  natural  action  of  boiling.  In 
this  case  the  water,  when  once  steam  is  formed,  is  constantly 


220  THE  PRACTICAL  PHYSICS  OF 

thrown  upwards  and  returns  by  gravity  to  the  lowest  level,  either 
with  regular  movement,  when  channels  are  provided  for  this 
return,  or  spasmodically,  when  steam  formation  is  allowed  to 
interfere  with  it. 

2.  That  which  is  forced  or  produced  by  mechanical  means, 
in  which  case  both  quantity,  speed  and  direction  can  be  wholly 
under  control. 

Natural  Circulation  by  Boiling. — Regarding  natural  circulation, 
as  produced  by  the  process  of  boiling  or  steam  production, 
numerous  theories  have  been  advanced  to  explain  certain 
phenomena  which  have  been  noticed  with  particular  boilers,  but, 
as  in  other  matters,  experimenters  have  forgotten  the  many  ways 
in  which  the  conditions  under  which  their  results  were  obtained 
might  be  altered,  and  have  too  hastily  formulated  "  rules  "  or 
"laws,"  for  general  application,  on  the  evidence  of  experiments 
too  few  in  number  and  too  limited  in  their  conditions. 

Clerk  Maxwell  on  "  Boiling."  -  —  No  explanation  of  the 
phenomena  of  boiling  could  be  more  simple  or  complete  than  that 
of  Professor  Clerk  Maxwell  (in  "  Theory  of  Heat,"  p.  23),  which 
is  as  follows  :  "  When  water  is  heated  in  the  ordinary  way,  by 
applying  heat  to  the  bottom  of  a  vessel,  the  lowest  layer  of  the 
water  becomes  hot  first,  and  by  its  expansion  it  becomes  lighter 
than  the  colder  water  above  and  gradually  rises,  so  that  a  gentle 
circulation  of  water  is  kept  up  and  the  whole  water  is  gradually 
warmed,  though  the  lowest  layer  is  always  the  hottest.  As  the 
temperature  increases,  the  absorbed  air,  which  is  generally 
found  in  ordinary  water,  is  expelled  and  rises  in  small  bubbles 
without  noise.  At  last  the  water  in  contact  with  the  heated 
metal  becomes  so  hot  that,  in  spite  of  the  pressure  of  the  atmo- 
sphere on  the  surface  of  the  water,  the  additional  pressure  due 
to  the  water  in  the  vessel,  and  the  cohesion  of  the  water  itself, 
some  of  the  water  at  the  bottom  is  transformed  into  steam, 
forming  a  bubble  adhering  to  the  bottom  of  the  vessel.  As  soon 
as  a  bubble  is  formed  evaporation  goes  on  rapidly  from  the 
water  all  round  it,  so  that  it  soon  grows  large  and  rises  from  the 
bottom.  If  the  upper  part  of  the  water  into  which  the  bubble 
rises  is  still  below  the  boiling  temperature,  the  bubble  is  con- 
densed, and  its  sides  come  together  with  a  sharp  rattling  noise, 
called  simmering.  But  the  rise  of  the  bubbles  stirs  the  water 
about  much  more  vigorously  than  the  mere  expansion  of  the 


THE  MODERN  STEAM  BOILER.  221 

water,  so  that  the  water  is  soon  heated  throughout  and  brought 
to  the  boil,  and  then  the  bubbles  enlarge  rapidly  during  their 
whole  ascent,  and  burst  into  the  air,  throwing  the  water  about 
and  making  the  well-known  softer  and  more  rolling  noise  of 
boiling."  Although  this  description  concerns  itself  primarily  with 
the  operation  of  boiling  in  an  open  vessel,  yet  it  applies  equally 
well  to  boiling  in  the  same  vessel  when  closed  and  under  pressure, 
as  practically  nothing  is  then  altered  but  the  comparative  volume 
of  the  bubbles  of  steam.  There  are  two  points  mentioned  in  the 
description  which  are  frequently  overlooked  by  other  observers, 
and  these  are — (i)  that  the  water  in  contact  with  the  heating 
surface  is  necessarily  hotter  than  the  rest  of  the  water  in  circu- 
lation, and  (2)  that  the  bubbles  of  steam  enlarge  as  they  ascend 
in  consequence  of  the  heat  of  the  steam  causing  evaporation 
from  the  surrounding  water,  as  soon  as  the  water  has  reached 
such  a  temperature  that  no  condensation  of  the  bubbles  takes 
place  during  their  ascent.  This  important  part,  which  is  played 
by  the  heat  of  the  steam  in  the  bubbles  is  constantly  overlooked. 
It  is  necessarily  absent  in  the  case  of  bubbles  of  air  blown 
through  the  water  in  experiments  (although  such  bubbles  may 
enlarge  slightly  on  account  of  diminution  of  pressure),  and  in 
that  of  glass  bubbles  and  corks,  which  are  also  used  to  illustrate 
the  action  of  bubbles  of  steam,  and  consequently  reasoning 
which  is  founded  on  phenomena  produced  with  such  apparatus 
must  be  to  some  extent  unsound. 

Clerk  MtLvwcIl  on  "  Convection  Currents" — More  particularly 
with  reference  to  the  diffusion  of  heat  in  fluids,  Professor  Clerk 
Maxwell  has  said  (op.  cit.  p.  230),  "  When  the  application  of  heat 
to  a  fluid  causes  it  to  expand  or  to  contract,  it  is  thereby 
rendered  rarer  or  denser  than  the  neighbouring  parts  of  the 
fluid  ;  and  if  the  fluid  is  at  the  same  time  acted  on  by  gravity, 
it  tends  to  form  an  upward  or  downward  current  of  the  heated 
fluid,  which  is,  of  course,  accompanied  by  a  current  of  the  more 
remote  parts  of  the  fluid  in  the  opposite  direction. 

"  The  fluid  is  thus  made  to  circulate,  fresh  portions  of  fluid  are 
brought  into  the  neighbourhood  of  the  source  of  heat,  and  these 
when  heated  travel,  carrying  their  heat  with  them  into  other 
regions.  Such  currents,  caused  by  the  application  of  heat  and 
carrying  this  heat  with  them,  are  called  convection  currents. 
They  play  a  most  important  part  in  natural  phenomena,  by 


222  THE  PRACTICAL  PHYSICS  OF 

causing  a  much  more  rapid  diffusion  of  heat  than  would  take 
place  by  conduction  alone  in  the  same  medium,  if  restrained 
from  moving.  The  actual  diffusion  of  heat  from  one  part  of  the 
fluid  to  another  takes  place,  of  course,  by  conduction  ;  but  on 
account  of  the  motion  of  the  fluid,  the  isothermal  surfaces  are  so 
extended,  and  in  some  cases  contorted,  that  their  areas  are 
greatly  increased,  while  the  distances  between  them  are 
diminished,  so  that  true  conduction  goes  on  much  more  rapidly 
than  if  the  medium  were  at  rest." 

Although  it  is  true,  as  Professor  Clerk  Maxwell  has  said,  that 
convection  currents  depend  on  changes  of  density  in  a  fluid  acted 
upon  by  gravity,  and  that,  were  gravity  absent,  there  would  be 
no  convection  currents,  yet  this  does  not  prove,  as  Mr.  Thorny- 
croft1  contended,  that  "  the  force  of  gravity  is  the  real  force  and 
the  only  force  we  have  to  depend  on  for  the  circulation  of  water 
in  the  boiler."  He  continues,  "  If  we  could  go  to  another 
planet,  where  the  force  of  gravity  was  larger,  we  might  have  less 
trouble  with  the  circulation  in  our  boilers.  On  the  other  hand 
if  we  could  take  the  boiler  down  to  the  centre  of  the  earth, 
where  gravity  may  be  supposed  to  be  nil,  or  acting  equally  in  all 
directions,  then  no  construction  of  boiler  that  we  could  adopt 
would  enable  us  to  make  one  that  would  work.  It  would  be 
sure  to  burn." 

Under  such  circumstances,  however,  other  conditions,  such  as 
those  of  combustion,  would  also  be  altered  and  if  no  movement 
of  air  could  be  obtained  (as  would  also  be  the  case),  howr  would 
the  fire — not  to  speak  of  the  boiler — burn  ?  In  addition  to  that, 
it  is  always  possible  to  rely  upon  mechanical  force  to  cause  circu- 
lation of  the  water  ;  and  in  any  case,  it  is  under  present  well- 
known  mundane  conditions  that  we  have  to  consider  the  efficient 
working  of  boilers. 

A  considerable  variety  of  forms  of  apparatus  has  been  used  in 
experiments  made  to  illustrate,  or  to  demonstrate,  certain  ideas 
connected  with  this  subject,  but  the  conclusions  drawn  from 
these  experiments  have  not  always  been  consistent  or  sufficiently 
conclusive. 

Matthews  Experiments — Action  of  Bubbles. — Two  experiments 
(which  were  excellent  specimens  of  a  class  of  such)  wrere 

1  Trans.  Inst.  N.  A.,  Vol.  xxxvii.,  pp.  135,  136. 


THE  MODERN  STEAM  BOILER.  223 

shown  by  Mr.  C.  A.  Matthey1  to  the  lost,  of  Engineers  and  Ship- 
builders in  Scotland  for  the  purpose  of  throwing  light  upon  the 
question  whether  the  presence  of  a  bubble  of  gas,  or  of  a  solid 
body  lighter  than  water,  immersed  in  a  column  of  water  and 
rising  through  it,  diminished,  or  did  not  diminish,  the  hydrostatic 
pressure  at  the  bottom  of  the  column.  A  vertical  glass  tube, 
2  inches  in  diameter  and  5  feet  high,  connected  at  the  bottom 
with  another  glass  tube  of  the  same  height,  but  only  one  eighth 
of  an  inch  in  diameter,  was  placed  vertically  upon  an  electro- 
magnet D,  as  shown  in  Fig.  98.  The  tubes  were  nearly  filled 
with  water,  and  a  glass  bubble  C,  a  little  smaller  than  the 
large  tube,  floated  within  it  with  the  water  level  at  B  B.  To  the 
bottom  of  the  glass  bubble  was  attached  a  small  piece  of  soft 
iron  which,  when  the  bubble  was  pushed  down  to  the  bottom  of 
the  tube,  caused  it  to  be  anchored  there  by  the  attractive  force 
of  the  electro-magnet.  When  the  bubble  wras  fully  immersed 
and  prevented  from  rising,  the  water  level  rose,  by  virtue  of  its 
displacement,  to  the  level  A  A,  the  pressure  on  the  bottom  being 
registered  by  the  level  of  the  water  in  the  small  gauge  tube.  On 
breaking  the  electric  circuit  through  the  magnet  D  the  bubble 
was  released  and  free  to  rise  in  the  tube.2  As  soon  as  it  moved 
the  water  level  began  to  fall  from  A  towards  B,  in  both  tubes, 
and  it  dropped  to  B  as  soon  as  the  bubble  had  attained  its  maxi- 
mum velocity  of  ascent.  "  This  showed/'  Mr.  Matthey  remarked, 
"  that  the  pressure  of  a  free  bubble  in  the  large  tube  made  the 
pressure  on  its  bottom  less  than  that  which  corresponded  to  the 
height  of  the  water  in  it."  It  may  be,  however,  that  the  apparent 
diminishing  of  the  hydrostatic  head  was  an  effect  due  to  setting 
the  water  in  motion,  as  it  is  undoubted  that  a  complex  system  of 
stream  lines  must  accompany  the  movement  of  the  bubble  through 
the  water. 

In  another  experiment  shown  with  a  U-tube,  Fig.  99,  the 
water  level  stood  at  E  E,  and  a  nozzle  and  pipe  were 
provided  at  F,  by  means  of  which  gas  or  air  could  be  blown 
into  the  left-hand  limb  of  the  U.  On  blowing  gas 'into  the  left- 
hand  limb  by  this  nozzle,  the  water  level  was  raised  by  the 

1  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland,  Vol.  xli.,  pp.  147-150. 

2  This  is  a  better  mode  of  procedure  than  has  been  usual  in  such  experiments. 
See  Trans.  Inst.  Marine  Engineers,  Vol.  x.,  No.  Ixxvii.,  page  24  ;  Engineering, 
Vol.  lx.,  p.  430,  Vol.  Ixi.,  p.  436. 


224 


THE  PRACTICAL  PHYSICS  OF 


bubbles  to  G  or  G^  but  the  level  in  the  right-hand  limb  remained 
at  E  ;  and  this  was  so,  whether  much  or  little  gas  was  forced 
into  the  tube.  Mr.  Matthey  held  that  this  demonstrated  that  the 
pressure  at  the  bottom  of  the  U-tube  was  the  same  as  if  the  gas 
were  absent,  and  he  added,  "  This  disposed  of  the  distinction 


m 

¥ 


FIG.   99. 


which  had  been  drawn  between  the  case  where  there  was  con- 
tinuity of  water  round  the  bubbles,  and  where  the  bubbles  made 
plugs  of  gas  and  water  alternately,  completely  occupying  the 
section  of  the  tube.  It  was  sometimes  said  that  the  water  was 
entrained  by  the  bubbles  ;  or  that  the  bubbles  rose  in  virtue  of 


THE     MODKRX  STKAM   BOILER.  225 

their  lightness  and  dragged  the  water  with  them.  Such  expres- 
sions were  loose  and  unscientific.1  The  bubbles  which  rose  in 
the  left-hand  leg  in  Fig.  99  did  not  drag  any  water  out  of  the 
other  leg.  But,  if  instead  of  the  bubbles,  a  solid  ball  attached 
to  a  line  wire  was  placed  at  the  bottom  of  the  left-hand  leg,  and 
drawn  upwards  by  means  of  the  wire,  the  level  in  the  right-hand 
leg  became  depressed,  while  in  the  left-hand  leg  it  rose.  This 
might  be  called  entrainment,  but  it  was  produced  by  an  external 
force,  not  by  the  mutual  action  of  the  water  and  the  immersed 
body." 

This  experiment  with  the  bubbles  shows  that  the  force  which 
impels  the  advance  and  ascent  of  the  bubbles  of  gas  in  one  limb 
of  the  tube  evidently  rc-ticls  to  prevent  any  alteration  of  the  head 
of  water  in  the  other  limb,  and  it  is  probable  that  the  same 
result  attends  the  formation  and  ascent  of  steam  bubbles  in  the 
same  apparatus.  This  is  a  different  action  from  that  supposed  by 
Mr.  Thorny  croft,-  in  which  periodical  accumulation  of  steam 
takes  place  in  the  tube  and  by  its  expansion  propels  the  water 
out  of  the  upper  end,  whilst  it  simultaneously  pushes  back  the 
water  at  the  lower  end  and  drives  some  of  the  water  out  of  the 
tube  in  that  direction. 

If,  however,  the  two  limbs  of  the  U-tube  be  joined  by  a  hori- 
xontal  tube  just  above  E,  the  water  which  is  forced  up  to  G  will 
then  run  across  by  the  horizontal  connection  to  the  right  hand 
limb,  down  which  it  will  How,  and,  thus  altering  the  hydrostatic 
head  at  that  point,  will  produce  a  movement  or  circulation  of  the 
water  in  the  U-tube.  It  is  evident  that  it  is  in  this  latter  form 
that  we  approach  the  conditions  which  ought  to  be  present  in 
boilers,  as  they  must  provide  not  only  for  the  free  escape  of  the 
steam  from  the  water,  but  also  for  the  due  return  of  the  water 
which  is  carried  along  by  the  steam. 

G///.SY-  of  Morcincnl  of  Water. — As  to  the  cause  of  movement 
iu  such  tubes,  there  is  a  variety  of  opinions.  Thus  in  one 
volume3  we  read,  "  If  the  water  is  as  shown  in  Fig.  100  and  the 
bubbles  of  steam  rising  in  it  as  shown,  the  bubbles  may  be  rising 
very  rapidly  and  producing  no  circulation,  for  the  head  of  the 

1  Sec  also  remarks  by  Mr.  C.  H.  \Vintfiield  in  Trans.  Inst.  Naval  Architects, 
Vol.  xxxvii..  pp.  2.S/,  2<SS. 

-  Min.  Proc.  Inst.  C.  E.,  Vol.  xcix.,  p.  46. 
"  Steam  Boilers,"  by  George  Halliday.     London,  1897,  p.  279. 

I 


226 


THE  PRACTICAL    PHYSICS  OF 


water  will  still  be  the  same  as  in  the  other  limb.  .  .  .  These 
bubbles  might  be  replaced  by  corks,  and  every  one  knows  that  a 
cork  rising  to  the  surface  will  not  produce  circulation."  But  at 
page  293  of  the  same  volume  we  have  some  account  of  experi- 
ments made  by  Professor  Watkinson  in  these  words  :  "  The  first 
kind  of  circulation,  viz.,  that  produced  by 

I 1     water  following  the  rising  of   the  steam 

bubbles  through  the  water,  is  illustrated  in 
Fig.  101.  There  the  steam  bubbles  do 
not  fill  the  base  of  the  left  tube,  nor  is 
there  any  foam  to  completely  fill  any  part 
of  the  tube,  and  the  movement  of  the 
water  is,  when  all  at  the  same  temperature, 
produced  entirely  by  the  entraining  action 
*  of  the  bubbles  of  steam.  A  further  proof 

(j  of  this  is  shown  in  Fig.  102,  where  a  tube 

I  is  inserted  inside  of  another,  and  a  bent 

blow-pipe  is  led  down  as  shown.     When 
FIG.  ioo.  air  is  blown  down  through  the  tube,  it 

rises    in    bubbles  -from  the    nozzle  at   C, 

producing  an  upward  movement  of  the  water  by  the  entraining 
action  of  the  bubbles.  .  .  .  The  circulation  is,  then,  not  pro- 
duced in  any  way  by  a  difference  in  density  between  the  tw-o 
vertical  limbs.  And  if  further  proof  be  needed,  it  is  supplied 
by  the  third  experiment,  Fig.  103,  where  the  movement  of  a 
number  of  beads,  threaded  on  a  wire  up- 
wards or  downwards,  makes  the  water  in 
the  tubes  follow  the  beads  upwards  or 
downwards  in  the  same  way  as  it  follows 
the  bubbles  of  steam  upwards  in  limb  A, 
Fig.  101." 

Here,  then,  we  have  two  diametrically 
opposite  opinions  given  by  two  authorities 
on  the  same  point  or  question.  It  says  much  FIG 

for  the  candour  of  the  author  of  one  of  them 
that  we  find  both  expressions  of  opinion  almost  side  by  side  in  the 
same  volume.  It  is  evident,  however,  that  we  must  refer  Fig.  103 
back  to  Mr.  Matthey's  experiment  on  p.  223,  and  to  the  difference 
shown  by  him  between  bubbles  of  gas  and  a  solid  ball  on  a 
fine  wire  in  Fig.  99.  There  is  no  fair  comparison  possible 


. 

I-  ".j^^.-;^—  -' 
^~'°-  ——^ 


THE  MODERN  STEAM  BOILER. 


227 


Vsl=  !>'- 


between  a  solid  piston  or  diaphragm,  of  whatever  size  or  shape, 
moved  by  external  force  in  a  liquid,  and  the  movement  of  free 
bubbles  of  air,  gas  or  steam,  in  the  same  mass  of  liquid.     As  to 
the  other  matter,  there  is  undoubtedly  some  movement  of  the 
water  produced  by  the  passage  of  the  bubbles  of  air  or  gas,  and, 
as    we    have    already   seen,   much    more 
disturbance  of  the  liquid  produced  by  the 
movement  of  bubbles  of  steam  which  we 
found  in  it,  but  whether,  under  the  cir- 
cumstances  supposed,  that  movement  is 
sufficient   to  provide  efficient  circulation 
in  a  boiler,  does  not  concern  us,  because 
the  conditions  are  not  those  of  the  rapid 
generation    of    steam,    and    intermediate 
stages  must  quickly  pass  till  this  one  is 
reached.       It    is    certain,    however,    that 
without  the  additional  movement  of  the 
water,  due   to  alteration  of   head  in  the 
down-comer,  the  movement  of  the  bubbles 
FIG.  I02.  alone  could  not  cause  any  general  circu- 

lation of  the  water  in  a  boiler. 

Additional  light  is  thrown  on  this  subject  by  the  paper,  "  On 
the  Ascent  of  Hollow  Glass  Bulbs  in  Liquids,"  read  by  Professor 
E.  J.  Mills,  D.Sc.,  F.R.S.,  to  the  Physical  Society  of  London,  on 
May  14,  1881,  and  published  in  the  Phil.  Mag.  in  July  of  that 
year.  Dr.  Mills  showed  the  effect  of  varia- 
tion of  the  diameter  of  the  tube  on  the 
speed  of  ascent  ;  also  the  effect  of  change 
in  the  amount  of  unbalanced  pressure,  to 
which  ascent  is  due  ;  and  also  the  effects 
of  having  gases  of  different  specific  gravity 
in  the  bulbs,  and  gave  an  algebraic  expres- 
sion of  the  law  under  which  in  each  case 
the  ascent  took  place. 

Action  of  Rapid  Formation  of  Steam. — When 

steam  is  being  rapidly  formed,  all  are  agreed  that  with  small 
tubes  or  passages  the  steam  bubbles  form  plugs  or  pistons  which 
practically  force  the  water  before  them,  and  in  effect  in  many 
boilers  produce  fairly  continuous  fountains  or  cascades  from 
almost  all  the  tubes  into  the  upper  chamber  of  the  boiler.  It  is 


1 

A    ' 

:-r—  T.—.  r^-~- 

;                 i 

FIG.   103. 


228 


THE  PRACTICAL  PHYSICS  OF 


quite  clear  that  gravity  is  not 
the  only  force  concerned  in 
ihis  result,  but  the  quantity  of 
water  so  thrown  up,  to  some 
extent  contrary  to  the  action 
of  gravity,  contributes  by  its 
descent  to  an  increased  gravity 
result,  and  otherwise  assists 
in  the  healthy  action  of  the 
boiler.  Fig.  104  illustrates  this 
phenomenon  in  a  boiler  of 
the  Thornycroft  pattern,  with 
water-tubes  delivering  above 
the  water  level  of  the  boiler. 

With  larger  tubes,  and  with 
FIG  tubes     nearly     horizontal,    it 

stands    to    reason    that    these 

plugs  or  pistons  can  rarely,  if  at  all,  be  formed,  and  in  such  case 
the  circulation  will  be  neither  so  rapid  nor  so  regular.    That  is  to 


MODEL  OF  BABCOCKANO  WILLCOX   BOILER 
FIG.    I  OS. 


say,  the  quantity  of  water  forced  into  movement  by  the  action  of 

the  steam  cannot  be  so  large.     In  some  cases  foam  is  formed,  but 

he  existence  of  foam  in  tubes  and  headers  is  most  undesirable 


THE  MODERN  STEAM  BOILER. 


229 


from  the  point  of  view  of  heat  transmission,  though  it  is  not  so 
bad  as  the  presence  of  a  large  quantity  of  steam  which  can 
escape  only  slowly,  whilst  it  prevents  the  entry  of  sufficient  water 
into  the  tube.  Yet  both  of  these  conditions  are  likely  to  exist  in 
boilers  of  the  inclined  tube,  and  Belleville  classes  with  large  tubes. 
Fig.  105  shows  one  of  these  conditions  in  an  inclined  tube 
boiler,  as  existing  in  a  model  in  action.  The  foam  appears  in 
the  header  and  at  the  top  ends  of  the  tubes.  The  model  of  a  Belle- 
ville boiler  exhibited  in  action  by  Professor  Watkinson l  during 


MODEL  Of  BELLEVILLE   BOILER 


a  discussion  on  water-tube  boilers  at  the  Institution  of  Engineers 
and  Shipbuilders  in  Scotland,  showed  a  considerable  quantity  of 
water  forced  into,  and  retained  in  the  steam  drum  (above  the 
normal  water-line  of  the  boiler),  and  some  of  the  inclined  tubes 
near  the  top  kept  almost  full  of  steam,  in  consequence  of  the 
water  which  had  been  forced  up  into  the  drum  being  unable  to 
re-enter  the  tubes  by  the  steam  passage.  This  model  is  shown 
in  Fig.  1 06.  In  discussing  the  subject,  as  illustrated  by  the  glass 

1  Sec  Trans.  lust.  ling,  and  Shipbuilders  in  Scotland,  Vol.  xli.,  pp.  249-255. 


230  THE  PRACTICAL  PHYSICS  OF 

models  on  the  occasion  referred  to,  it  was  remarked1  that  "  tak- 
ing the  indications  given  by  the  action  of  Professor  Watkinson's 
glass  models,  the  Belleville  boiler  ought  to  have,  on  Professor 
Watkinson's  basis  of  reasoning,  the  best  circulation,  because  it 
showed  the  largest  quantity  of  water  forced  up  the  greatest 
distance  into  the  drum  above  the  water  level.  But  it  really 
shoxved  the  worst  circulation,  because  that  water  (the  position 
of  which  really  constituted  Professor  Watkinson's  gauge  of  the 
amount  of  circulation)  was  maintained  there  at  the  expense  of 
the  upper  rows  of  tubes,  which  were  kept  nearly  empty  of 
water,  and  thus  exposed  to  over-heating  and  to  easy  distortion 
by  strains,  such  as  those  caused  by  the  pitching  and  rolling  of 
steam  vessels."  The  observations  recorded  in  Chap.  II.,  pp. 
45-48  show  that  there  is  some  foundation  for  the  opinion 
that  such  action  really  takes  place  in  this  boiler. 

Where  plugs  or  pistons  of  steam  are  not  formed,  there  is  a 
continuous  stream  of  bubbles  rushing  upwards,  always  accom- 
panied by  more  or  less  water,  which  is,  as  Clerk  Maxwell  re- 
marked, thrown  up  into  the  steam  space. 

Down-comers. — It  is  no  doubt  the  proper  course  in  boiler 
design  to  provide  distinct  channels  or  passages  wrhich  are  to  be 
used  as  down-comers  only,  where  the  circulation  is  that  produced 
by  boiling,  so  that  the  water  carried  up  may  descend  continuously 
without  any  interruption  from  the  formation  of  steam  in  the 
down-comer  passages.2  This  is  sufficiently  apparent  to  be  axiom- 
atic, as  is  also  the  principle  that  in  water-tube  boilers  the  more 
nearly  vertical  the  water  passages  (for  both  up  and  down 
currents)  are,  the  more  truly  are  they  arranged  in  harmony  with 
the  laws  of  the  circulation  of  heated  fluids.  These  principles 
the  author  advocated  and  defended  in  a  series  of  letters  to 
Engineering3  in  1877,  and  in  spite  of  the  popularity  of  some 
boilers  constructed  of  water-tubes  only  slightly  inclined  from  the 
horizontal,  it  is  certain  that  the  best  results  can  never  be  reached 
by  any  compromise  with  fundamental  principles.  The  experi- 
ments described  by  Mr.  John  Watt  to  the  Institution  of  Naval 

1  §ee  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland,  Vol.  xli.,  p.  127. 

2  See  Trans.  Inst.  X.  A.,  Vol.  xxxvii.,  p.  287,  288. 

3  See  Engineering,  I3th  and  2Oth  April,  4th,  nth,  and  i8th  May,  ist  June 
and  20th  July,  1877,  also  "  On  the  Design  and  Use  of  Boilers,"  Engineering, 
Vol.  xxvi.,  164. 


THE  MODERN  STEAM  BOILER.  231 

Architects1  in  March,  1896,  are  as  inconclusive  on  this  point  as 
are  the  first  two  bold  assertions  which  he  called  "rules "or 
''  laws  "  in  his  paper  of  March,  1874,  from  which  he  quoted  them 
with  approval  for  the  instruction  of  the  Institution  of  Naval 
Architects.  If  it  is  ridiculous  to  expect  a  good  result  from  a 
Cornish  boiler  placed  on  end,  as  Mr.  Watt  once  contended,2 
how  much  more  so  to  expect  a  Root  boiler  or  a  Babcock  and 
Wilcox  boiler  to  work  at  all  when  placed  with  the  water-tubes 
in  a  vertical  position.  They  would  then  possess  no  proper 
means  of  being  either  heated  or  supplied  with  water,  and  no 
competent  person  could  compare  them,  under  such  circum- 
stances, with  any  water-tube  boiler  properly  constructed  with 
vertical  \vater-tubes.  The  defects  in  Mr.  Watt's  reasoning  from 
his  experiments  were  demonstrated  by  Mr.  Thornycroft  and 
Mr.  Blechynden  in  Trans.  Inst.  N.  A.,  Vol.  xxxvii.,  pp.  182-284 ; 
and  by  Mr.  Normand's  paper  "  On  Water-Tube  Boilers"  in  the 
same  volume,  p.  109. 

Regarding  the  use  of  separate  down-comers,  it  seems  to  be 
held  by  some  makers  that  boilers  composed  of  nearly  vertical 
water-tubes  which  deliver  steam  below  water  level,  under  the 
ordinary  method  and  conditions  of  firing,  are  sure  to  have  some 
of  the  tubes  kept  exposed  to  a  very  much  higher  temperature 
than  others  which  are  farther  from  the  fire,  and  that  the  water 
will  descend  by  these  cooler  tubes,  even  when  no  regular  down- 
comer  is  provided,  in  spite  of  the  fact  that  these  tubes  are 
exposed  to  some  heating.  Mr.  W.  M.  McFarland  records 3 
that  some  years  ago  Mr.  C.  Ward,  in  America,  announced  that 
he  did  not  find  external  down-comer  tubes  to  be  necessary. 
"  As  a  matter  of  necessity,"  he  said,  "  some  tubes  will  be  cooler 
than  others,  and  if  the  water  goes  up  in  some,  it  must  come 
down  in  others.'1  There  appears  to  be,  however,  rather  too  much 
haphazard  in  this  plan,  which  practically  allows  the  boiler  to 
choose  for  itself  which  are  to  be  its  down-comer  passages  ;  and  it 
is  quite  conceivable  that  such  a  change  of  conditions  might 
arise  in  the  course  of  working  as  would  upset  the  ordinary 
sequence  of  the  actions  depended  upon,  and  interfere  with  the 
safety  of  the  boiler,  or,  in  any  case,  seriously  diminish  its 

1  Trans.  I.  N.  A.,  Vol.  xxxvii.,  p.  261. 

2  See  Engineering,  May  25,  1877. 

3  Trans.  Inst.  Engineers  and  Shipbuilders  in  Scotland,  Vol.  xli.,  p.  138. 


THE  PRACTICAL  PHYSICS  OF 


efficiency.  With  ordinary  arrangements  for  tiring,  and  with 
natural  circulation  of  the  water  due  to  the  action  of  boiling,  a 
boiler  might  continue  to  work  steadily  for  some  time,  under  such 
conditions  as  Mr.  Ward  indicated,  but  a  stress  of  circumstances 
might  arise  at  any  moment  which  would  destroy  the  equilibrium 
of  the  apparatus,  so  that  Mr.  Ward's  plan  could  not  be  reckoned 
upon  as  a  very  satisfactory  one.  A  little  more  heat  than  usual 
getting  to  the  tubes  acting  as  down-comers  might  interrupt  the 
current  of  water  by  the 
formation  of  steam  in  them, 
and  might  thus  force  the 
water  to  remain  in  the 
upper  portions  of  the  boiler 
till  some  damage  was  done 
by  the  overheating  of  tubes. 

Mr.  Yarrow's  Experiments 
on  Down-comers. — Mr.  A.  F. 
Yarrow,  however,  carried 
out  some  very  interesting 
experiments  which  show 
that  it  may  be  possible  to 
heat  the  down-comers  of  a 
boiler  without  interfering 
with  the  direction  of  the 
current  of  wrater.  These 
experiments  are  shown  in 
the  following  illustrations 
and  described  in  Mr.  Yar- 
row's words.  "  Fig  107  FK;  j(r 
represents  a  glass  U-  tube, 

the  upper  extremities  being  fixed  to  a  chamber  containing  water. 
At  the  top  will  be  seen  a  balance,  at  one  end  of  which  is 
a  thin  cord  with  a  bob  attached,  this  bob  being  immersed  in  one 
of  the  columns.  Any  circulation  of  water,  by  acting  on  the  bob, 
would  be  indicated  by  the  balance.  It  will  be  seen  that  there 
are  three  lamps  on  each  side,  adapted  for  heating  the  two  tubes. 
In  Fig.  107  the  three  lamps  on  one  side  are  alight  and  circula- 
tion in  this  tube  is  naturally  set  up  in  an  upward  direction 
drawing  the  water  down  the  tube  on  the  opposite  side. 

"  After  this  circulation  was  started  the  three  lamps  heating  the 


THE  MODERN  STEAM  BOILER. 


233 


other  tube,  see  Fig.  108  (that  is,  the  one  in  which  the  water 
was  moving  downwards),  were  lighted,  and  it  was  found, 
contrary  to  general  opinion,  that  the  circulation  was  not  stopped 
or  retarded,  but  actually  accelerated,  as  will  be  seen  by  the 
position  of  the  balance  in  Fig.  108.  "  Some  further  trials  were 
made  with  a  similar  apparatus,  but  on  a  larger  scale,  under 
pressures  varying  from  50  to  150  Ibs.  per  square  inch,  and  it 
was  found  that  when  once  circulation  was  set  up  in  a  certain 

direction,  all  the  heat  might 
be  applied  to  the  dowrn 
current  without  reversing 
the  circulation,  which  thus 
remained  constant.  This 
was  a  result  quite  unex- 
pected. It  was  thus  proved 
that  when  once  circulation 
is  set  up,  it  has  a  very 
strong  tendency  to  remain 
constant." 

Mr.  Yamnv's  conclusion 
from  these  experiments  is 
scarcely  sufficient  basis  for 
proof  of  the  larger  question 
involved.  The  general  con- 
clusion, that  the  direction 
of  circulation  or  movement 
of  water  when  once  set  up 
tends  to  remain  constant,  is, 
no  doubt,  correct,  because 
in  order  to  alter  the  direc- 
tion more  force  has  to  be  brought  to  bear  on  the  water  than  is 
required  to  set  up  the  movement  in  the  rirst  instance.  The  already 
established  movement  has  to  be  stopped  and  reversed.  The  same 
result  is  seen  in  the  experiments  with  air  bubbles,  described  by 
M.  de  Chasseloup-Laubat1  and  others,  where  the  action  of  heat 
does  not  enter  into  the  question.  But  the  conclusion  that  when 
once  circulation  is  set  up  in  a  certain  direction  all  the  heat  may 

1  Sec  Lcs  Chaudieres  Marines  par  M.  de  Chasseloup  Laubat,  in  Mem.  de  la 
Sue.  des  Ingenieurs  Civils  de  France,  April,  1897.  See  also  Trans.  Inst. 
Engineers  and  Shipbuilders,  Vol.  xli.,  p.  2=53. 


FIG.    108. 


234  THE   PRACTICAL  PHYSICS  OF 

be  applied  to  the  down-comer  without  reversing  the  direction, 
cannot  with  safety  be  applied  to  boilers  in  actual  operation.  The 
reason  is  apparent.  In  the  case  of  tubes  or  models  heated  by 
gas  flames,  both  the  amount  of  heat  and  the  part  of  the 
surface  to  which  it  is  applied  suffer  no  fluctuation,  and  moreover 
the  amount  of  heat  is  not  great  and  it  is  completely  under 
control  from  moment  to  moment.  The  conditions  are  entirely 
different  in  the  case  of  boilers  with  coal  fires,  operated  either  by 
natural  or  forced  draught.  The  temperature  is  constantly  varying 
from  a  far  more  fierce  heat  than  that  of  Bunsen  flames  to  a  low 
degree,  and  the  eddying  of  the  currents  of  gases  causes  unequal 
and  varying  distribution  of  the  heat.  Moreover,  the  opening  of 
furnace  doors  alone  is  sufficient  to  cause  a  radical  alteration  of 
the  conditions.  In  such  a  case  it  would  be  far  from  prudent  to 
trust  to  the  continued  or  regular  action  of  such  down-comers, 
which  could  at  almost  any  moment  be  thrown  entirely  out  of  gear. 
In  reasoning  from  the  results  of  experiments  it  is  necessary  always 
to  give  due  consideration  to  the  altered  conditions  of  actual 
work,  but  this  is  frequently  forgotten.  Where,  however,  a 
boiler  is  composed  of  several  rows  of  small  tubes  it  is  probable 
that  the  three  or  four  rows  nearest  to  the  fire  will  screen  off  the 
heat  from  the  outer  rows,  shading  them  from  the  radiation  and 
interposing  their  large  amount  of  surface  to  cool  down  the  hot 
gases  before  these  reach  the  outside  rows.  It  is  in  just  such  a 
boiler  as  that  of  Mr.  Yarrow  that  such  a  result  is  most  likely  to 
be  experienced  and  his  latest  experiments  l  show  how  he  has 
taken  advantage  of  it  and  has  even  advanced  a  step,  so  that  by 
admitting  the  feed  water  to  these  tubes  he  constitutes  them  a 
feed-heater  for  the  supply  of  the  boiler. 

Chasseloup-Laubat's  Summaiy. — A  very  useful  summary  of 
elementary  experiments  on  circulation  of  wTater  in  boilers  is 
given  by  M.  de  Chasseloup-Laubat  in  his  excellent  treatise  on 
Les  Chaudieres  Marines*  (pages  76-94). 

Bellens1  Experiments. — Amongst  the  most  interesting  are  some 
with  models  prepared  by  M.  C.  Bellens  and  described  in  his 
work  on  steam  boilers.3  M.  Bellens  prepared  two  models  with 

1  Trans.  Inst.  N.  A.,  Vol.  xl.  (March  3ist,  1898.) 

2  Published  in  Memoires  de  la  Societe  des  Ingenieurs  Civils  de   France. 
April,  1897. 

3  Traite  des  Chaudieres  a  Vapeur,  par  Charles  Bellens.     Paris,  1895. 


THE  MODERN  STEAM  BOILER. 


235 


tubes  respectively  of  25  millimetres  and  60  millimetres  diameter, 
slightly  inclined  from  the  horizontal.  These  are  shown  in  Figs. 
109  and  no. 


Regard 


Glace. 


Regard 


entde 
-Niveaud'eau.          /lavapeur 


FIG.   IIO. 


In  the  first  (Fig.  109)  the  water  was  free  to  circulate  in  either 
direction,  and  the  arrows  show  the  course  which  it  usually  took. 


236 


THE  PRACTICAL  PHYSICS  OF 


In  the  second  model  (Fig.  no)  means  were  introduced  by  which 
either  the  upper  or  lower  extremity  of  the  inclined  tubes  could 
be  closed  at  will.  M.  Chasseloup-Laubat  testifies  that  in  these 
forms  the  circulation'  was  very  middling — as  M.  Bellens  had  also 
remarked  in  his  interesting  volume — and  that  a  considerable 
part  of  the  water  set  in  motion  by  the  steam  bubbles  returned 
by  the  upper,  instead  of,  as  ought  to  have  been  the  case,  by  the 
lowrer  end  of  the  tubes.  Moreover,  the  movement  of  the  water 
in  the  second  and  third  tubes  from 
the  bottom  was  extremely  irregular. 
Not  only  was  it  fast  or  slow  without 
apparent  reason,  but  also  it  changed 
in  direction,  and  sometimes  the  tubes 
were  almost  entirely  filled  with  steam. 
These  disturbances  were  produced 
chiefly  at  the  moment  when  any  varia- 
tion of  the  heating  took  place.  At 
A,  B,  and  C  (Fig.  no)  a  considerable 
space  along  the  upper  sides  of  the 
tubes  is  shown  with  steam  only  in 
contact  with  the  tube  surfaces.  This 
is  commonly  seen  in  models  having 
inclined  tubes,  and  reveals  the  possi- 
bility of  overheating  which  is  often 
found  in  boilers  constructed  -on  that 
plan. 

"  Eimtlseiir"  Tubes. — Fig.  in  shows 
an  apparatus,  also  constructed  by  M. 
Bellens,  to  illustrate  the  action  of  the  FIG.  m. 

"  emulseurs  "  introduced  by  M.  Dubiau 

for  the  purpose  of  producing  a  more  active  and  forcible  circula 
tion  of  the  water  than  that  which  is  due  only  to  the  action  of 
gravity.  Two  globes,  A  and  B,  are  joined  by  a  tube  K,  and  by 
another  tube  E,  of  which  latter  the  lower  end  is  bevelled.  The 
tube  E  is  called  the  u  emulseur  "  tube.  On  commencing  to  work, 
the  lower  globe  B  is  completely  filled  with  water,  and  then  heat 
is  applied  to  it.  The  st'eam  accumulates  in  the  upper  portion  of 
B,  depressing  the  water  level  until  the  edge  of  the  bevel  P  is 
reached.  The  steam  then  escapes  by  the  tube  E,  and  in  doing 
so  forces  water  up  into  the  globe  A.  From  that  moment  an 


THE  MODERN  STEAM   BOILER.  237 

extremely  active  circulation  is  set  up.  The  level  of  the  steam 
remains  constant  unless  the  rate  of  heating  is  such  that  more 
steam  is  formed  than  can  escape  by  the  tube  E.  In  this  latter 
case  \ve  arc  not  told  what  would  happen,  but  may  readily 
imagine  what  the  result  would  be  ;  and  it  is  thus  apparent  that 
the  safety  of  such  apparatus  depends  entirely  upon  having  a 
sufficient  area  of  "  emnlsenr  "  tubes  to  provide  for  variations  in 
the  rate  of  steam-raising. 

ThornverotVs  Experiment. — Mr.  ].  I.  Thornycroft,  in  two  papers 
presented  to  the  Institution  of  Naval  Architects,1  described  some 
interesting  experiments  made  by  him  with  a  view  to  establish 
the  superiority  of  boilers  having  water-tubes  delivering  their 
steam  above  the  normal  water  level  of  the  boiler,  over  those 
boilers  whose  tubes  delivered  under  the  water  level.  The  tubes 
of  this  latter  form  of  boiler  are  sometimes  called  "  drowned  "  or 
immersed  tubes  ;  and  M.  de  Chasseloup-Laubat  has  placed  the 
two  kinds  of  boilers  respectively  under  classes  which  he  terms 
"non-reversible  cycle"  and  "  reversible  cycle"  boilers.  Mr. 
Thornycroft  carried  out  these  experiments  in  apparatus  repre- 
sented by  Figs.  112  and  113,  and  described  them  as  follows: 
"  Considering  the  boilers  shown  in  Figs.  112  and  113,  if  the  pres- 
sure in  the  lower  vessel — that  is,  at  the  bottom  ends  of  the 
generating  tubes — is  that  due  to  the  full  depth  of  water  in  the 
boiler,  in  addition  to  the  steam  pressure,  then  any  reduction  of 
density  in  the  generating  tubes  will  all  be  available  for  causing 
circulation  ;  and  thus  any  reduction  in  pressure  in  the  lower 
vessel,  below  that  due  to  the  head  of  water  in  the  boiler,  is  a 
direct  loss  to  the  energy  of  circulation,  so  that  variations  of  this 
pressure  are  of  great  importance.  These  variations  can  be 
conveniently  measured  by  a  pressure  column  formed  of  a  long 
gauge  glass  connecting  the  steam  space  of  the  upper  vessel  with 
the  lower  vessel.  The  difference  of  the  water  level  in  this  glass 
from  the  water  level  in  the  upper  vessel  is  a  direct  measure  of 
any  reduction  of  pressure  in  the  lower  vessel. 

"  I  have  made  experiments,  taking  observations  from  such 
pressure  columns  fitted  to  the  boilers  shown  in  Figs.  112  and  113 
when  they  were  working  under  different  conditions.  The  rate 

1  On  "  Circulation '  in  the  Thornycroft  Water-tube  Holler,"  Vol.  xxxv., 
p.  287.  On  "The  Influence  ot  Circulation  on  Evaporative  Efficiency  of 
\Valer-tube  Hollers,"  Vol.  \\.\vi.,  p.  40. 


THE  PRACTICAL  PHYSICS  OF 


FIG.   113- 


THE  MODERN  STEAM  BOILER.  239 

of  evaporation  and  steam  pressure  being  varied  for  the  several 
arrangements  of  boiler,  which  were — 

"  (i)  Generating  tubes  delivering  above  water. 

"  (2)  Generating  tubes  delivering  below  water. 

"  (3)  Generating  tubes  delivering  below  water  without  any 
special  clown  take  tube. 

"The  curves  in  diagram  Fig.  114  show  graphically  the  results 
of  these  experiments  ;  the  falls  of  pressure  in  the  lower  vessels 
are  plotted  as  ordinates,  and  the  rates  of  working  as  abscissae. 

"  It  will  be  seen  that  the  rate  of  working  has  been  taken  up 
very  high,  probably  more  than  double  ordinary  working,  the 
object  in  doing  this  being  to  ascertain  up  to  what  rate  each 
arrangement  can  be  worked  with  safety. 

"  In  the  first  series  of  curves,  the  results  recorded  were 
obtained  from  the  boiler  (Fig.  112)  with  the  generating  tubes 
delivering  above  water.  It  will  be  seen  from  the  curve  that,  as 
the  rate  of  working  is  increased,  the  pressure  column  falls 
slightly,  and  at  an  evaporation  of  20  Ibs.  of  water  per  square 
foot  of  heating  surface  stands  at  85  per  cent,  of  the  maximum  ; 
and  by  halving  the  working  pressure  the  results  are  not  sensibly 
changed. 

"  The  next  series  of  curves  is  taken  from  the  boiler  (Fig.  113), 
which  has  the  same  heating  surface,  etc.,  as  Fig.  112,  but  the  top 
ends  of  the  tubes  deliver  below  water.  It  will  be  seen  that  the 
curves  fall  much  more  rapidly  than  the  first  series,  and  that  by 
halving  the  working  pressure  the  pressure  in  the  lower  vessel 
is  distinctly  reduced.  The  third  series  was  obtained  from  the 
same  boiler  (Fig.  113)  by  plugging  the  down-tubes,  so  that  some 
of  the  generating  tubes  had  to  act  as  down-tubes  for  the  supply 
of  the  others  ;  the  feed  water  being  all  delivered  into  the  upper 
vessel.  In  this  case  the  character  of  the  curves  changes  from 
the  first  two  series  very  much.  A  diminution  in  pressure  of 
working  causes  the  pressure  column  to  fall  very  much  ;  in  the 
case  of  the  pressure  being  only  28*75  Ibs.  Per  square  inch 
absolute,  it  fell  to  about  46  per  cent,  of  the  maximum. 

"  The  most  important  point,  however,  apart  from  this  low 
pressure,  but  a  result  of  it,  is  that  for  any  given  pressure  a 
critical  rate  of  working  is  arrived  at  \vhen  the  pressure  column 
begins  to  rise  again  with  increased  rate  of  working,  thus 
showing  an  increased  pressure  in  the  lower  vessel,  caused  by  the 


240  THE  PRACTICAL  PHYSICS  OF 

steam  being  unable  to  get  out  at  the  top  ends  of  the  tubes  fast 
enough,  and  so  comes  out  at  the  bottom  ends  as  well. 

"  It  will  be  seen  from  the  curves  that  the  lower  the  pressure 
of  working  the  sooner  this  critical  point  is  arrived  at,  and  I 
found  that  when  the  evaporation  was  pushed  beyond  this  critical 
point  the  tubes  were  not  safe  from  overheating  ;  but,  by  taking 
the  tubes  intended  for  downtakes,  and  extending  their  upper 
ends  above  the  water  surface  so  that  water  could  not  go  down, 
and  the  steam  in  the  lower  vessel  could  readily  get  away  to  the 
separator,  it  was  possible  to  increase  the  rate  of  evaporation 
somewhat,  inasmuch  as  the  facility  for  the  tubes  getting  rid  of 
their  steam  was  increased. 

"  Contrasting  the  different  conditions  of  working  of  the  water- 
tubes  in  the  three  series  of  experiments  I  have  described,  and 
noting  what  slight  differences  these  conditions  may  necessitate 
in  the  design  of  a  boiler,  the  nearness  to  success  which  a  boiler 
intended  for  hard  forcing  may  be,  and  yet  fail,  is  clearly  seen. 

"  In  conclusion,  I  would  submit  that  the  absence  of  special 
down-  tubes  limits  to  a  great  extent  the  amount  to  which  a  boiler 
can  be  safely  forced,  and  shows  that  to  obtain  the  highest  rate 
of  working  with  safety  and  efficiency  these  special  down-tubes 
must  not  be  neglected  ;  and  still  further,  the  tubes  should  cleliver 
above  water,  as  then  the  circulation,  as  I  have  previously  shown, 
is  double  that  when  the  tubes  deliver  below  water.  So  that  this 
rapid  circulation  is  a  most  important  condition  for  hard 
working." 

In  his  previous  paper  (read  in  March,  1894),  Mr.  Thornycroft 
said  that  he  had  "  recently  made  experiments  on  the  relative 
circulation  of  boilers  when  the  generating  tubes  deliver  above 
the  water  in  the  separator  and  below  it,"  and  had  "  found  that, 
in  the  case  where  they  deliver  above,  the  circulation  is  rather  more 
than  double  that  when  they  deliver  below."  u  The  method 
of  measurement  I  adopted,"  he  continued,  "  was  to  put  a  rect- 
angular notch,  similar  to  those  usually  employed  in  gauging 
small  streams,  across  the  separator,  so  that  all  the  water  that 
went  down  the  downtakes  had  to  pass  over  it,  and  I  then 
observed  the  flow  over  the  notch  through  a  glass  window  in  the 
end  of  the  boiler,  and  thus,  knowing  the  size  of  the  stream,  was 
able  to  calculate  the  circulation.  I  found  that,  in  the  case  of 
the  above-water  delivery,  the  circulation  was  105  times  the 


THE  MODERN  STEAM  BOILER.  241 

feed — that  is  to  say,  for  every  pound  of  steam  brought  up  by  the 
generating  tubes,  105  pounds  of  water  are  also  passed  through 
them."  This  was,  however,  modified  at  a  later  date  by  Mr. 
Thornycroft  saying1  that  " //  the  water  going  down  the  small 
In hcs,  which  should  not  go  down,  was  neglected,  the  How  in  the 
tubes  delivering  above  water  was  about  twice  as  great  as  the 
How  in  the  tubes  delivering  below."  This  .  is  an  important 
qualification,  for  it  is  only  in  the  boiler  with  tubes  delivering 
below  water  that  any  water  could  go  down  the  small  tubes,  and 
it  is  impossible  to  say  how  many  of  these  might  act  (or  might 
have  acted)  as  down-comers  during  such  experiments,  or  what 
effect  that  might  have  on  the  rate  of  How  of  water  towards  the 
downtake  tube  at  the  end  of  the  separator.  On  this  account  the 
conclusion  as  to  the  proportionate  How  of  water  in  the  two 
instances  <is  observed  is  not  very  convincing  ;  and  another 
element  of  uncertainty  is  added  in  the  fact  of  the  How  of  water 
having  to  be  observed  end-on  (i.e.,  in  the  line  of  and  not  across 
the  line  of  advance  of  the  water)  from  the  glass  window  in  the 
end  of  the  separator,  under  circumstances  in  which  a  regularly 
flowing  stream  could  not  be  expected,  whilst  all  variations  in 
speed  of  the  current  had  to  be  estimated  by  the  eye  in  the 
position  mentioned. 

The  measurement  of  flowing  water  by  means  of  bays  or 
weirs  is  in  reality  a  very  delicate  operation,  and  there  are 
numerous  sources  of  error  connected  with  it.  The  coefficients 
differ  with  the  depths  of  water,  the  width  of  canals  of  ap- 
proach, the  depths  from  the  bottom  of  canals  to  the  bottom 
edges  of  the  weirs,  the  length  and  thickness  of  the  weirs,  and 
other  circumstances.  We  have  it,  for  instance,  on  the  authority 
of  Messrs.  Donkin  and  Salter,2  that  an  error  of  -^y  of  an  inch 
in  excess  (in  measurement  of  the  head  of  water  over  the  bay  in 
his  experiments)  in  reading  with  ij>  inch  of  water  running  over 
the  bay  would  have  increased  the  theoretical  quantity  by  o'2  per 
cent. 

Xonnrtnd's  Objections. — M.  Xormand  dissented  from  the  con- 
clusions founded  on  these  experiments  on  other  grounds.  He 
said3 : — "  With  all  due  deference,  may  I  be  allowed  to  state  that 

1   See  Trans.  Inst.  X.  A.,  Vol.  xxxvii.,  page  137. 

-  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixxxiii.,  380.     See  also  Ixxix.,  402  ;  cxiv.,  333. 
"();i  Water  tube  Boilers."     Trans.  Inst.  X.  A.,  Vol.  xxxvii.,  page  112. 


242  THE  PRACTICAL  PHYSICS  OF 

I  draw  from  these  trials  entirely  opposite  conclusions  ?  The 
dimensions  of  the  outside  return  tubes  being  similar  in  both 
cases,  and  admitting  that  the  total  return  of  water  takes  place 
by  these  tubes,  and  not  partially  through  some  of  the  heating 
tubes  which  may  be  less  exposed  to  the  fire  (which  does  not 
seem  to  be  a  very  reliable  arrangement),  it  is  clear  that  the 
quantity  of  water  which  goes  down  through  the  return  tubes 
will  be  proportional  to  the  square  root  of  the  difference  oi 
pressure  between  both  reservoirs.  Now,  this  quantity  of  water 
is,  by  hypothesis,  exactly  equal  to  the  ascending  water,  so  that 
it  is,  according  to  the  trials,  greater  in  the  boiler  where  the 
upper  ends  of  the  tubes  are  under  water.  This  conclusion  is  in 
accordance  with  the  following  probable  theory,  that  the  head 
of  water  which  causes  the  circulation  in  a  tube  rising  above 
water  must  be  reduced  by  a  height  equal  to  that  of  the  tube 
above  the  water  level,  due  allowance  being  made  for  the  smaller 
density  of  the  fluid.  The  under-water  arrangement  does  not, 
perhaps,  allow  of  so  great  a  heating  surface  for  a  given  encum- 
brance, but  it  offers  the  further  advantage  that  no  '  steam 
chamber  '  can  exist  in  the  upper  part  of  the  tubes." 

There  are,  in  fact,  other  elements  which  should  also  enter 
into  the  consideration  of  such  a  question.  For  instance,1  in  the 
two  boilers  experimented  with,  the  distance  between  the  upper 
and  lower  vessels  was  least  where  the  length  of  the  bent  water- 
tubes  was  greatest  in  one  boiler,  and  vice  versa  in  the  other. 
That  is  to  say,  in  the  one  which  showed  the  smallest  fall  of 
water  level,  the  water  had  the  longer  distance  to  ascend  and  the 
shorter  to  return,  whilst  the  other  presented  the  opposite  con- 
ditions. It  is  evident  that  the  variation  of  water  level  was 
caused  by  a  more  rapid  circulation  in  the  boiler  which  showed 
the  greatest  fall  in  the  test  column,  unless  we  are  to  believe  that 
longer  and  more  crooked  tubes  offer  less  resistance  to  the  flow 
of  water  than  the  shorter  and  straighter  ones. 

The  slower  the  circulation,  the  larger  the  quantity  of  water 
which  would  be  comparatively  quiescent  in  the  lower  vessel  or 
chamber,  and  therefore  able  to  maintain  the  water  column  at  its 
original  level.  But  if  all  the  water  were  in  rapid  and  violent 
circulation,  that  would  in  effect  be  equal  to  an  enlargement  of 

1  "  On  Water-tube  Boilers,"  by  F.  J.  Rowan.  Trans.  Inst.  Engineers  and 
Shipbuilders  in  Scotland,  Vol.  xli.,  p.  29. 


I     !    I     I 

fSSft     tl*  INCHfS  OF  WATf* 


THE  MODERN  STEAM  BOILER.  243 

the  steam  space,  because  a  large  quantity  of  the  water  would  be 
always  broken  up  into  the  state  of  foam,  and  this  would  lower 
the  level  in  the  test  column.  It  seems  to  be  clear  that  in  neither 
of  these  cases  could  the  test  column  be  taken  as  the  equivalent 
of  a  piezometer. 

Since  the  above  was  written,  the  view  therein  expressed  has 
been  fully  confirmed  by  a  paper  read  to  the  Inst.  C.  E.  by  Mr. 
J.  T.  Milton,  Chief  Engineer  Surveyor  of  Lloyd's  Registry.1 
Mr.  Milton  says  of  these  experiments  of  Mr.  Thorny- 
croft's  :  "  In  the  experiments  made  at  two  different  steam 
pressures  and  at  rates  of  evaporation  varying  between  3lbs.  to 
over  i5lbs.  per  hour  per  square  foot  of  heating  surface,  the 
reduction  of  pressure  in  the  lower  chambers  was  in  every  case 
from  two  and  a  half  to  three  times  as  great  in  the  boiler  where 
all  the  tubes  delivered  below  the  water  as  in  that  in  which  they 
delivered  above  the  water.  The  velocity  of  the  water  in  the 
down-comers  must,  therefore,  have  been  between  60  per  cent. 
and  70  per  cent,  greater  in  the  former  than  in  the  latter,  and 
therefore  far  more  water  must  have  circulated  through  the  up- 
tubes.  This  should  have  been  expected,  as  in  the  boiler  with 
the  above-water  delivery,  owing  to  the  greater  height  the 
mixture  of  steam  and  water  has  to  be  raised,  its  density  must  be 
lighter,  or  the  pressure  to  raise  it  must  be  greater,  or  both  of 
these  must  act  together.  A  lower  density  with  the  same  amount 
of  steam  evolved  must  imply  less  water  circulating  with  the 
steam." 

Blechynden's  Experiments. — It  was  known  that  the  late  Mr. 
Blechynden  was  engaged  on  some  experiments  on  circulation  of 
water  in  boilers,  the  results  of  which,  it  was  feared,  would  have 
been  lost  to  the  profession  in  consequence  of  his  untimely  death. 
Happily,  however,  Mr.  Milton,  in  his  paper  on  "  Water-tube 
Boilers  for  Marine  Engines  "  (Min.  Proc.  Inst.  C.  E.,  Vol.  cxxxvii., 
pp.  178-180),  places  on  record  an  account  of  these  experiments 
obtained  from  Mr.  Billetop,  who  carried  out  the  work  for  Mr. 
Blechynden.  Mr.  Milton  says  :  "  These  trials  are  especially 
valuable  because  they  were  made  upon  a  full-sized  boiler,  not  upon 
models.  The  boiler,  Fig.  115,  had  a  grate  surface  of  37  square 
feet,  and  a  total  heating  surface  of  2,445  square  feet.  Besides  the 

1  On  "  Water-tube  boilers  for  Marine  Engines."  Min.  Proc.  Inst.  C.  E., 
Vol.  cxxxvii.,  p.  167. 


244 


THE  PRACTICAL  PHYSICS  OF 


small  generating  tubes,  which  were  one  inch  in  external  diameter, 
the  upper  and  lower  chambers  were  connected  by  eight  stay-tubes, 
ij  inches  internal  diameter,  which  were  placed  outside  the 
casing,  and  which  could  not  be  shut  off  nor  plugged,  and  also 
by  a  5-inch  internal  diameter  down-pipe  to  each  bottom 
chamber,  these  being  so  arranged  that  they  could  be  shut  off 
when  required.  The  feed-water  could  be  delivered  either  into 
the  upper  chamber,  through  an  ordinary  full-length  perforated 
internal  feed-pipe  entirely  submerged,  or  into  the  two  lower 
chambers,  which  were  also  fitted  with  internal  pipes.  Special 
gauge-glasses  were  fitted,  as  shown  in  Fig.  115,  to  allow  the 


/     1 


KU;.  115. 

direction  of  the  current  in  the  outer  rows  of  tubes  to  be 
observed,  and  also  to  show  the  reduction  of  pressure  in  the 
lower  chamber  under  the  different  conditions  of  the  various 
experiments.  So  far  as  feeding  was  concerned  three  distinct 
sets  of  experiments  were  made  :  (i)  with  the  feed  in  the  upper 
chambers  ;  (2)  with  the  feed  in  the  lower  chambers  ;  and  (3) 
with  the  feed  shut  off  entirely  ;  the  last  experiments,  however, 
could  be  made  for  short  periods  of  three  minutes  or  four 
minutes  only. 

"  When  the  feed  is  delivered  into  the  upper  chamber  it  mixes 
with  the  water  there,  which  is  at  the  boiling  point,  and  comes 
into  contact  with  some  of  the  steam  generated,  so  that  before  it 
reaches  the  down-coming  tubes  its  temperature  will  be  raised 


THE  MODERN  STEAM   BOILER.  ^45 

considerably,  possibly  to  nearly  the  boiling  point.  If  any  of 
the  generating  tabes  act  as  down-comers,  the  water  in  them  will 
be  further  heated  on  its  way  to  the  bottom  chamber,  so  that  the 
temperature  of  the  water  in  the  bottom  chambers  may  be  nearly 
that  of  the  boiling  point.  When,  however,  the  feed  enters  the 
lower  chambers  direct,  the  water  in  them  will  be  of  considerably 
lower  temperature  than  boiling  point.  If  the  feed  is  shut  off 
for  a  few  minutes  all  the  water  in  the  boiler  will  be  raised  to  the 
boiling  point.  If  the  water  first  entering  the  up-tubes  is  at 
boiling  point  steam  bubbles  will  be  formed  in  these  tubes  along 
their  whole  length,  whereas  if  the  water  enters  at  a  less  tem- 
perature, the  first  part  of  the  length  of  the  tubes  will  be  occupied 
in  raising  the  temperature  of  the  water  to  boiling  point,  and 
only  in  that  part  of  the  tube  above  this  will  bubbles  be  formed. 
The  average  density  of  water  in  the  up-tube  will  therefore  be 
greater  when  the  feed  is  placed  in  the  lower  chambers,  and 
there  will  be  less  reduction  of  pressure  in  the  lower  chambers. 
Another  way  of  considering  the  matter  is  that  when  the  feed 
enters  the  lower  chambers  all  the  steam  produced  in  the  tubes 
is  available  for  the  engine;  while  when  it  enters  the  upper 
chamber,  some  part  of  the  steam  made  in  the  tubes  is  employed 
in  heating  the  feed-water  nearly  up  to  the  boiling  point.  In  the 
latter  case,  therefore,  with  the  feed  in  the  upper  chamber,  if  the 
output  of  the  boiler  is  the  same  there  will  be  more  steam,  and, 
consequently,  relatively  less  water  in  the  generating  tubes.  This 
will  cause  a  greater  loss  of  pressure  in  the  lower  chamber. 

"  The  actual  results  of  loss  of  pressure  in  this  lower  chamber 
during  a  series  of  experiments  made  with  this  boiler  are  shown 
in  Fig.  116.  Curve  No.  i  gives  the  results  of  four  experiments 
made  at  different  rates  of  evaporation  with  the  special  down- 
pipes  open,  and  the  feed  entering  at  the  bottom.  No.  2  gives 
the  results  of  two  experiments  under  similar  conditions,  but  with 
the  feed  entering  the  top  chamber,  while  No.  3  gives  the  results 
of  trials  made  with  the  feed  shut  off  for  short  periods.  It  will 
be  seen  that  all  three  curves  are  slightly  convex  downwards,  in 
this  respect  being  similar  to  those  representing  Air.  Thorny- 
croft's  results.  The  fall  of  pressure  in  the  lower  chamber,  due 
to  introducing  the  feed  in  the  top  chamber,  is  very  marked. 
Curve  No.  4  gives  the  results  of  three  experiments  made  with 
the  special  down-comers  shut  off  and  the  feed  entering  at  the 


246 


THE  PRACTICAL  PHYSICS  OF 


top.     The  difference  between  curves  No.  2  and  No.  4  is  there- 
fore due  entirely  to  the  effect  of  the  large  outside  pipes. 

lt  In  all  the  experiments  the  gauge-glass  D,  Fig.  115  showed 
that  in  the  wall-tubes  the  current  was  downwards  when  the  water 
level  was  above  their  upper  ends.  It  was  also  always  downwards 
in  the  glass  C  in  all  three  experiments  without  the  outside  large 
tubes,  and  in  the  other  experiments  it  was  generally  downwards 
also,  as  only  on  one  or  two  occasions  was  the  current  observed 
to  be  reversed.  When  the  outside  tubes  were  shut  off  and  the 
boiler  was  much  forced  for  a  few  minutes,  the  feed  entering  the 
top  and  the  water  maintained  at  the  ordinary  level  in  the 
ordinary  gauge-glass,  the  water  in  gauge-glass  B  fell  out  of  sight 


FIG.  116. 

altogether,  and  an  accumulation  of  steam  was  formed  in  the 
lower  chamber.  This  was  demonstrated  by  opening  a  cock 
fitted  to  the  chamber,  but  it  is  needless  to  state  that  this  experi- 
ment was  not  continued  very  long." 

Mr.  Milton  remarks  that  "  there  is  difference  of  opinion  as  to 
the  advantage  or  necessity  of  a  high  speed  of  circulation  of  the 
water  in  a  water-tube  boiler  ;  but  that  it  is  agreed  that  the 
inner  surfaces  of  the  tubes  should  always  be  kept  wet  to  prevent 
overheating,  so  that  a  considerable  proportion  of  water  should 
always  be  in  them  and  not  steam  alone,  especially  in  those  tubes 
exposed  to  the  fiercest  action  of  the  fire."  Mr.  Blechynden's 
experiment  of  forcing  the  boiler,  without  the  large  down-tubes, 
showed  that  "  at  very  high  rates  of  evaporation  there  is  a 


THE  MODERN  STEAM  BOILER. 


247 


possibility  of  all  the  water  being  driven  out  of  some  of  the  tubes, 
but  it  will  require  much  greater  forcing  to  do  this  when  large 
down-tubes  are  fitted  or  when  the  feed  is  entered  into  the  lowrer 
chambers."  In  actual  trials  at  sea  with  the  Blechynden  type 
of  boilers,  "  at  high  powers  there  was  a  considerable  amount  of 
priming  when  the  feed  was  entered  in  the  upper  chamber. 
After  the  feed  pipes  were  altered  to  enter  the  lower  chambers, 
there  was  no  further  trouble  in  this  respect." 

Appliances  for  Measuring  Circulation. — No  satisfactory  appli- 
ances for  the  measurement  of  the  quantity  of  water  circulating  in 
given  time,  or  for  indicating  the  velocity  of  the  wrater  circulating 
under  the  action  of  the  natural  process  of  boiling,  have  as  yet 
been  introduced.  Mr.  Thornycroft's  method  has  just  been  re- 
ferred to.  Another  was  introduced  in  1881  by  Mr.  Thielmann.1 
This  consisted  of  a  fan  or  propeller  wheel  fixed  in  the  rear  circu- 
lating tube  or  dowrn-comer  of  a  Steinmiiller  form  of  boiler.  The 
relative  dimensions  of  down-comer  and  propeller  are  unfortunately 
not  given,  but  it  is  stated  that  under  test  the  propeller  for  each 
100  revolutions  passed  40  litres  of  water.  When  the  boiler  was 
under  steam,  the  propeller  revolved  at  the  rate  of  from  380  to 
420  revolutions  per  minute,  showing  that  from  152  to  168  litres2 
of  water  were  passing  through  it  per  minute.  This  was  equal  to 
from  7-5  to  8-4  litres  per  square  metre  of  heating  surface'.  The 
actual  evaporation  of  the  boiler  was  20  kilos 3  per  hour  per 
square  metre  of  surface,  which  amounted  to  about  4^5  per  cent, 
of  the  water  circulated.  The  total  quantity  of  water  contained 
in  the  boiler  was  450  litres,  which  quantity  was  circulated  every 
three  minutes.4  This  is  a  very  interesting  method  of  observing 
the  circulation,  but  it  is  evident  that  it  demands  that  no  water 
shall  descend  by  any  other  passage  than  the  appointed  down- 
comer.  It  has  also  the  disadvantage  that  the  propeller  cannot 
be  put  out  of  action  except  by  removing  it  from  the  boiler,  which 
necessitates  the  opening  up  of  the  boiler.  To  be  thoroughly 
serviceable  such  apparatus  should  be  capable  of  being  rapidly 

1  "  Handbuch  iiber  Vollstiindige  Dampfkessel  Anlangen."  See  Mr.  G.  W. 
Thode's  remarks  in  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland,  Vol.  xli., 
p.  142. 

-  i  litre  =  2'2O  Ibs.of  water  at  62°  F.,  or  '220  of  a  gallon. 

3  i  kilogramme  =  2-2046  Ibs. 

4  Mr.   G.   \V.   Thodc  was  kind   enough    to    furnish    the    author    with    this 
information. 


248  THE  PRACTICAL  PHYSICS  OF 

connected  with  and  disconnected  from  the  interior  of  the  boiler, 
and  should  introduce  the  minimum  of  parts  or  obstructions 
there. 

The  gauge  -  glass  system  for  indicating  the  difference  of 
pressure  between  the  top  and  bottom  chambers  of  a  boiler 
would,  if  it  could  be  relied  upon,  answer  these  requirements  in 
a  satisfactory  way.  But  neither  in  the  form  in  which  Mr. 
Thornycroft  introduced  it  in  the  experiments  referred  to,  nor  in 
the  modification  shown  by  Professor  Watkinson  is  it  sufficiently 
free  from  probable  error. 

The  latter  was  illustrated  and  explained  to  the  Institution  of 
Engineers  and  Shipbuilders  in  Scotland  l  as  follows  :  "  This 
was  shown  in  Fig.  117,  and  consisted  of  an  upper  and  a  lower 
drum  connected  by  one  down-comer  a  b  and  one  up-comer  c  d  c. 
Open-topped  gauge-columns  £  and  £r ,  were  fixed  to  the  upper 
and  lower  drums  respective!}'.  The  column  g  showed  the  level 
of  the  water  in  the  upper  drum,  and  column  »}  measured  the 
pressure  in  the  lower  drum.  When  circulation  was  set  up  by 
applying  heat  to  the  up-comer,  or  by  admitting  air  to  the  lower 
end  of  the  up-comer,  the  surface  of  the  water  in  the  column  ^' 
would  fall,  and  it  was  evident  that  the  difference  between  the 
levels  of  the  water  in  the  two  gauge-columns  was  the  head 
available  for  circulation  if  the  temperature  in  the  columns  had 
been  maintained  the  same.  If  the  temperature  of  the  water  in 
the  columns  had  not  been  maintained  the  same,  then  a  correction 
had,  of  course,  to  be  made  on  that  account.  As  the  corrected 
difference  of  levels  was  the  head  available  for  circulation,  the 
velocity  of  flow  through  the  clown-comer  was  proportional  to  the 
square  root  of  the  corrected  difference  of  level.  The  mass  of 
water  that  flowed  through  the  down-comer  per  second  was 

=  v/  2gh  x  A  x  C  x  M  Ibs. 

h   being  the  corrected  difference  of  levels  in  feet. 
A  being  the  area  of  the  down- comer  in  square  feet. 
C  being  the  coefficient  of  discharge  for  the  pipe. 
M  being  the  mass  of  I  cubic  foot  of  water  in  Ibs. 

In  the  experiments  which  he  (Professor  Watkinson)  had  made, 
in  order  to  eliminate  possible  errors  in  the  determinations  of  A, 

1  Transactions,  Vol.  xli.,  pp.  250-252.  See  also  Trans.  Inst.  X.  A.,  Vol.  xxxvii., 
pi.  xlviii..  Fig.  7. 


THE  MODERX  STEAM  BOILER. 


249 


M,  and  C,  he  had  disconnected  the  up-comer  d  e,  plugged  the 
hole  £,  and  then  syphoned  hot   water   into    the    upper    drum, 


FIG.    117.— WATKINSON's   KXI'KRIMKXTS  OX  CIRCULATION'. 

allowing  it  to  flow  out  of  an  adjustable  orifice  at  d.  By  adjust- 
ing the  size  of  the  orifice  at  </,  it  was  possible  to  reproduce  any 
deflection  of  the  gauge-column  gl  which  had  been  obtained  in 


250  THE  PRACTICAL  PHYSICS  OF 

the  ordinary  experiments.  By  proceeding  in  this  way,  and 
weighing  the  water  which  flowed  out  at  d,  he  had  been  able  to 
determine  very  accurately  the  mass  of  water  flowing  through 
the  down-comer  per  second,  for  different  deflections  in  the 
gauge-column  gl.  In  that  way  he  had  found  that  the  ratio  of 
the  mass  of  water  circulating  per  second,  to  the  mass  evaporated 
per  second,  varied  in  the  model,  at  the  usual  ratio  of  working, 


from  about        to  about  -        according  to  the  size  of  the  down- 

comer  used.  When  the  latter  value  was  obtained,  the  area  of 
the  down-comer  was  approximately  equal  to  the  area  of  the 
up-comer.  He  had  also  used  the  same  model  in  order  to 
determine  whether  there  was  any  gain  in  the  velocity  of  the 
circulating  water  due  to  discharging  that  water  above  the  wrater 
level  into  the  upper  drum.  .  .  .  He  had  found  that  when 
the  usual  ratio  of  area  of  up-comer  to  area  of  down-comer  was 
adopted  there  appeared  to  be  a  gain  of  3  or  4  per  cent,  in 
favour  of  the  above-water  discharge." 

Defects  in  Watkinson's  Apparatus.  —  "  Open-topped  gauge- 
columns  "  are,  of  course,  applicable  only  to  boiler  models  or 
boilers  worked  at  atmospheric  pressure,  but  even  for  such 
applications  it  is  not  'at  all  certain  that  as  registers  of  "  pressure," 
or  more  properly  of  hydrostatic  head,  they  would  always  give 
indications  which  could  be  relied  upon.  If,  for  instance,  the 
area  of  the  discharge  orifice  were  greater  than  that  of  the 
down-comer,  the  level  of  water  in  the  gauge-glass  gl  connected 
with  the  bottom  chamber  would  necessarily  fall,  and  that  gauge- 
glass  might  even  be  almost  empty,  but  that  would  result  from 
inadequacy  of  supply  to  the  bottom  chamber.  Where  that 
chamber  had,  however,  a  sufficient  capacity  such  a  result  would 
be  prevented.  In  fact  it  is  apparent  that  the  capacity  of  that 
chamber  must  exercise  the  greatest  influence  on  the  indications 
of  the  said  gauge.  Prof  essor  Watkinson  admitted  that  the  area  of 
the  down-comer  exerts  a  decided  influence  on  the  result,  so  that 
the  more  that  area  is  diminished  from  equality  with  that  of  the 
up-comer  the  smaller  is  the  velocity  of  circulation.  But  as  the 
experiment  with  the  plugged  up-comer  and  the  water  flowing 
out  at  d  (simply  by  gravity)  shows,  the  gauge-glasses  can  at  the 
best  indicate  only  the  rate  at  which  the  water  descends,  so  that 
we  might  readily  have  a  case  in  which  more  water  was  being 


THE  MODERN  STEAM  BOILER.  251 

carried  up  by  ebullition  than  \vas  able  to  flow  down  by  the 
dowrn-comer  in  a  given  time,  and  hence  the  gauge-glasses  would 
give  a  false  indication  of  the  condition  of  circulation  where  such 
elements  were  present. 

Theory  of  the  Piezometer. — There  does  not  seem  to  be  any  good 
reason  why  the  velocity  should  not  be  directly  measured  in 
relation  to  the  pressure  which  is  due  to  the  motion  of  the  water. 
It  is  well  known  that  the  hydrostatic  pressure  in  a  pipe  con- 
taining still  water  can  be  shown  by  inserting  an  open  tube  of 
any  shape  in  the  pipe.  The  water  rises  in  the  tube  to  a 
height  h,  whence  the  pressure  is  known  to  be  P  =  wh  Ibs.1 

If,  however,   the  water  is  flowing  with  a  velocity  V  in  the 
direction  of  the  arrow,  and  two  tubes  shaped  respectively  as 
A  B  and  C  D  in  Fig.  118  are  inserted  in  the  pipe,  then  there  will 
be  a  difference  of  level  in  these  tubes,  that 
in  A  B  being  lower  than  C  D.    The  difference 
of  level  between  C  and  A  has  been  found  to 


J8 


V 


be   — -    (feet)  but  "  the  real  pressure  in  the 

pipe  is  shown  by  the  tube  A  B,  and  the 
extra  height  of  the  column  in  C  D  is  due  to 
the  fact  of  the  still  water  in  C  D  at  its  open 
end  stopping  the  flow  of  the  water  which 
FIG.  us.  meets  it,  just  as  the  hand  held  still  in  a 

running  stream  stops  some  water,  and  hence 
a  pressure  is  felt.  If  there  were  no  loss  of  head,  C  would 
be  then  on  the  same  level  as  the  water  surface  of  the  reservoir. 
The  tube  A  B  is  called  a  piezometer,  and  we  must  always  be 
careful  to  see  that  it  is  quite  parallel  to  the  direction  of  flow."  - 

1  P  =  pressure  per  sq.  foot  due  to  head. 
w  =  weight  of  i  cubic  foot  of  water  in  Ibs. 
/;  =  height  in  feet  (i.e.  "  head  "). 
P  =  wh  Ibs. 

i  cubic  foot  of  fresh  water  weighs  62*5  Ibs. 
i  cubic  foot  of  sea  water  weighs  64  Ibs. 
Thus  a  head  of  i  ft.  of  fresh  water  =  62-5  Ibs.  per  square  foot. 

=  _L  Ibs.  per  square  inch. 

i  ft.  of  sea  water  =J_  Ibs.  per  square  inch. 

2-25 

i  inch  of  mercury  =  -49  Ib.  per  sq.  inch. 

-  Cotterill  and  Slade,  "Lessons  in  Applied  Mechanics,"  p.  475.     London, 
Macmillan,  1891 . 


252  THE  PRACTICAL  PHYSICS  OF 

Torricelli's  Theorem.  —  Professor  Greenhill  remarks  in  his 
"  Treatise  on  Hydrostatics  "  that,  a  the  velocity  v  of  discharge  of 
water  from  a  small  orifice  a  depth  h  below  the  free  surface  was 
given  by  Torricelli  (1643)  as  the  velocity  v  acquired  in  falling 
from  the  level  of  the  free  surface,  so  that 

±v*=gh,  orv=</(2gk) 

and  v  is  then  called  the  velocity,  due  to  the  head  h.  This  is 
argued  by  asserting  that  the  hydrostatic  energy  of  the  water  D/z 
foot-lbs.  per  cubic  foot,  or  h  foot-lbs.  per  lb.,  becomes  converted, 
on  opening  the  orifice,  into  the  kinetic  energy 

4  Dtflg  ft.-lb./ft.3,  or  i  v'/g  ft.-lb./lb. 

Bernoulli's    Theorem.  —  In    Bernoulli's   Theorem    the  gradual 

interchange  of  the  energies  due  to  pressure,  head  and  velocity  in 

a  stream  line  filament  in  the  interior  of  the  liquid,  or  in  a  smooth 

pipe  of  gradually  varying  section,  is  expressed  by  the  equation— 

p  +  Dx  +  ±  Eh>2=D/j,  a  constant, 

g 

i>  v*    , 

or  £  +x+  T  —hi  a  constant, 
D  'g 

when  p  denotes  the  pressure,  D  the  density,  v  the  velocity, 
and  x  the  height  above  a  fixed  horizontal  plane.  Thus,  with 
British  units,  the  total  constant  energy  Dh  along  a  stream  line 
is  in  foot-lbs.  per  cubic  foot,  and  composed  of  p  due  to  the  pres- 
sure, D.v  to  the  head,  and  -* —  due  to  the  velocity  ;  or  in  foot- 

o 

Ibs.  per  lb.  the  energy  or  head  h  is  composed  of  ~±-  due    to    the 

pressure,  .v  to  the  head,  and  \  i<2/g  to  the  velocity. 

u  Bernoulli's  Theorem  is  illustrated  experimentally  in  Fig.  119 
by  an  apparatus  devised  by  Froude '  ;  a  tube  of  varying  section 
carries  a  current  of  water  between  two  cisterns  filled  with  water 
to  nearly  the  same  level,  and  the  pressure  is  measured  by  the 
height  of  water  in  small  vertical  glass  tubes  called  piezometer2 

1  British  Association  Reports,  1875. 

-  For  piezometers  consult  Proc.  American  Academy  of  Arts  and  Sciences  ; 
"  Experiments  upon  Piezometers  used  in  Hydraulic  Investigations,"  by  Hiram 
F.  Mills,  Civil  Engineer,  Vol.  xiv.,  page  26  ;  Min.  Proc.  Inst.  C.  E.  Ixi.  408. 
See  also  "Experimental  Investigation  of  the  Theory  of  the  Pitot Tube,"  etc., 
by  A.  Rateau,  Prof,  at  the  School  of  Mines,  St.  Elienne,  Annales  des  Mines, 
1898,  series  9,  Vol.  xiii.,  p.  331  ;  also  Trans,  of  the  Inst.  of  Mining  Engineers, 
Vol.  xvii.  p.  124. 


THE  MODERN  STEAM  BOILER. 


253 


K 


254  THE  PRACTICAL  PHYSICS  OF 

tubes  ;  and  it  is  found,  in  accordance  with  Bernoulli's  Theorem, 
that  the  water  stands  higher  where  the  cross  section  of  the 
current  is  greater,  and  the  velocity  consequently  less."  This  is 
a  possible  explanation  of  the  differences  of  level  in  the  gauge- 
glasses  in  Mr.  Thornycroft's  experiments,  though  it  is  difficult  to 
see  how  these  columns  form  true  piezometers.  (<  If  the  velocity 
at  the  throat  E  is  that  given  by  Torricelli's  Theorem,  the  pres- 
sure there  is  reduced  to  atmospheric  pressure,  and  the  tube  can 
be  removed  in  the  neighbourhood  of  E,  as  at  the  throat  of  an 
injector  jet.  At  M  the  cross  section  is  less  than  at  E  and  the 
pressure  is  below  atmospheric  pressure,  so  that  water  will  be 
drawn  up  in  a  curved  piezometer  tube,  like  a  syphon.  By 
the  observation  of  the  heights  in  piezometer,  at  L  and  N  as  well, 
the  velocity  of  flow  can  be  inferred,  knowing  the  cross  section 
of  the  current."  • 

A  very  simple  explanation  of  this  last  point  is  given  in 
Cotterill  and  Slade's  "  Applied  Mechanics."  Taking  the  case  of 
a  pipe,  shown  in  Fig.  120,  the  section  of  which  varies  gradually, 
tubes  A  B,  C  D,  A1  B1  and  C1  D1  are  placed  in  it,  and  by  means 
of  these  the  changes  of  velocity  and  pressure,  which  take  place 
on  account  of  the  sectional  area  not  being  constant,  are  shown, 
although  the  whole  pipe  is  subject  to  the  same  "  head." 

"  Let  V  =  velocity  at  60,^  =  velocity  at  B1  D1 

A  =  sectional  area  at  B  D,  A1  =  sectional  area  at  B1  D1 

Then  the  most  plainly  evident  thing,  perhaps,  that  we  know 
about  the  flow  is  that  exactly  as  much  water  must  flow  past 
B  in  one  second  as  flows  past  D  in  the  same  time,  and  hence 

V  A  =  V1  A1, 

so  that  if  \ve  know  the  velocity  at  any  one  point  of  a  given  pipe, 
we  can  at  once  determine  it  for  any  point  whatever. 

Next  C  and  C1,  being  both  on  the  level  of  the  water  surface  in 

V* 
the  reservoir,  are  both  on  the  same  level.       But  A  is  feet 

2  g 

V'2 
below  C,  while  A1  is  only feet  below  C1  ;  whence  it  follows 

3£ 

that  A1  is  (V2 — V'2)/2£feet  above  A,  and  the  pressure  at  B1, 
which  would  in  still  water  be  greater  than  at  B  by  an  amount 
w  z — supposing  B1  to  be  z  feet  below  B,  i.e.,  the  head  over  B1  z 


THE  MODERN  STEAM  BOILER. 


255 


F.J.ROWAN'S   PIEZOMETER 
CIRCULATION     GUAGE 


256  THE  PRACTICAL  PHYSICS  OF 

feet  more  than  over  B — is  now  still  further  increased  by  the 
pressure  due  to  (V- — \"')/2g  feet  of  head. 

"  If  the  pipe  be  level,  then  z  vanishes,  and  we  see  that  in  a  level 
pipe  the  pressure  increases  as  the  velocity  diminishes,  i.e.  as  the 
sectional  area  increases.  This  result  appears  at  first  sight  strange, 
and  is  often  disputed  by  persons  not  properly  acquainted  with 
the  elements  of  the  subject.  The  objection  is,  of  course,  based 
on  a  misapprehension,  being  usually  put  something  in  this  form  : 
In  the  small  part  of  the  pipe  the  water  must  be  more  crowded 
together,  and  hence  the  pressure  must  be  greater.  The  idea 
present  here  is  plainly  that  of  a  crowd  of  people  moving 
through  a  narrow  passage  between  broader  spaces,  and  where 
the  analogy  fails  is  in  the  fact  that  the  velocity  does  "not  increase 
through  the  narrow  part  ;  those  behind  actively  push,  which  we 
must  remember  a  particle  of  water  cannot  do,  and  thus  prevent 
those  in  the  narrow  part  from  moving  at  a  rapid  rate." 

Now,  although  all  these  illustrations  and  arguments  are  con- 
cerned only  with  open-topped  pipes  at  atmospheric  pressure, 
yet  there  seems  to  be  no  reason  why  the  same  action  should  not 
take  place  where  both  the  tubes  are  subjected  to  the  same  steam 
pressure. 

Rowan's  Velocity  Gauge. — Fig.  121  shows  an  instrument 
devised  by  the  author)  by  which  the  velocity  of  the  current  of 
water  in  the  part  to  which  the  tubes  are  attached  may  at  any 
time  be  read  off. 

It  is  founded  on  a  direct  application  of  the  theory  of  the  piezo- 
meter to  the  problem  in  hand.  Between  the  gauge-glasses  con- 
nected with  the  piezometer  tubes,  which  have  a  common 
connection  above  to  the  steam  space,  there  is  a  movable  scale, 
divided  into  inches  and  parts  of  an  inch  on  one  side,  with  the 
corresponding  velocities  inserted  opposite  these  figures  worked 
out  according  to  the  formula,  v  =  J  2gli.  The  quantity  of 
water  flowing  per  second  can  readily  be  ascertained  from  this 
when  the  sectional  area  of  the  tube  or  passage  with  which  the 
gauge  is  connected  is  known. 

M.  Chasseloiip-Laubat's  Calculations. — M.  L.  de  Chasseloup- 
Laubat  published  an  examination  of  the  principles  of  circulation 
in  as  far  as  they  applied  to  water-tube  boilers,  of  what  he  termed 
"  reversible  "  and  "  non-reversible  "  cycle  classes,  in  which  the 
movement  of  the  water  was  that  which  was  produced  by  the 


UNIVERSITY 
THE  MODERN  STEAM  BOILER.  7257 

X^gAL^jKgiX 

natural  action  of  boiling.  The  following  summary  of  his  ex- 
amination of  the  subject  was  communicated  by  its  author  to  the 
Institution  of  Engineers  and  Shipbuilders  in  Scotland  :— 

(1)  "  In  a  liquid  of  known  scientific  weight,  a  bubble  of  steam 
of  known   specific  weight  and  volume,   occupying   a    position 
situated  at  a  known  distance  from  the  free  surface  of  the  liquid, 
corresponds  to  a  determined  potential  energy. 

(2)  "  The  yield  of  this  potential   energy  in  circulating  work 
when  the  bubble  rises  to  the  surface — i.e.,  the  useful  work  (from 
the  point  of  view  of  circulation)  resulting  from  the  transforma- 
tion of  this  potential  energy — is  not  constant.      It  is,  on  the 
contrary,  variable.     It  is  equal  to  the  theoretic  work  multiplied 
by  a    coefficient  varying  between  o  and  i.     This  coefficient  is 
itself  given  by  a  very  complex  function  of  numerous  elements, 
such  as  absolute  diameter  of  the  tubes,  absolute  diameter  of  the 
bubbles,  quality  of  the  water,  intensity  of  the  heating,  etc.     I 
have  only  been  able   to    show  the  existence  of  this  complex 
function  without  managing  to  determine  the  relative  value  of  its 
constituent  elements. 

(3)  ^  I    have    divided    the   water-tube    generators   into    two 
principal  classes,  which  I  have  termed   '  reversible  '   cycle  and 
'  non-reversible  '  cycle,  according  as  the  tubes  heated  have  their 
outlet  below  or  above  the  free  surface  of  the  water  in  the  upper 
collector. 

(4)  "I  have  shown  that  for  the  reversible  cycles  the  normal 
circulation  \vas  always  continuous,  whilst  for  the  non-reversible 
cycles  it  \vas  generally  pulsatory. 

(5)  "  I  have  shown  that,  leaving  out  of  account  the  friction  and 
supposing  the  case  of  plug  bubbles  almost  completely  closing 
the   tube,  the  maximum  weight  of  fluid — steam   and  water — 
discharged  in  given  time  per  unit  of  section  of  heated  tube  was 
attained.     That  is  a  new  argument  in  favour  of  the  use  of  very 
high  working  pressures,  and  a  means  of  calculating  the  maximum 
of  specific  heating  compatible  with  the  security  of  the  apparatus. 
If   this   maximum  volume  of  steam  be  exceeded  in    the  tube 
heated,  the  circulation  may  become  irregular  and  pulsatory  and 
diminish    in    intensity,    in   which   case    the   apparatus  may  be 
endangered. 

(6)  "  For  the  non-reversible  cycles,  theory  and  experiments 
together   show    that    continuous    circulation     can    hardly    exist 


258  THE  PRACTICAL  PHYSICS  OF 

except  with  certain  qualities  of  water — brackish,  for  example — 
which  facilitate  the  formation  of  a  sort  ot  emulsion  or  intimate 
mixture  of  water  with  a  very  great  number  of  very  persistent 
little  bubbles.  More  generally,  with  ordinary  water,  the  circula- 
tion is  -pulsatory — that  is,  it  is  effected  by  alternate  discharges 
of  plugs  of  water  and  of  steam,  or,  more  correctly,  by  plugs  of 
steam  separated  by  a  mixture  of  water  and  steam.  In  this  case 
I  have  not  been  able  to  calculate  the  maximum  of  circulation. 

(7)  "  The  conclusion  is,  that  (a)  the  first  cause  of  all  circulation 
is  evidently  the  potential  energy  of  gravity,  resulting  from  the 
formation  of  bubbles  of  steam  in  the  midst  of  the  liquid  mass. 
(b)  The  rule  of  mean  specific  weights — which  evidently  gives 
the  work  available  to  produce  the  circulation — does  not  give  the 
effective  work  which  produces  this  circulation.  The  second  is 
equal  to  the  first,  multiplied  by  a  coefficient  varying  between 
o  and  i.  It  is  this  which  explains  why,  in  certain  water-tube 
apparatus  of  faulty  construction,  the  general  circulation  is  almost 
nil,  all  the  available  work  being  absorbed  by  local  eddies  and 
not  by  general  circulation. 

"  This  part  of  my  theory  has  lately  received  an  important 
experimental  confirmation.  M.  Bellens,  whose  studies  upon 
circulation  are  well  known,  has  published  in  the  Revue  Technique 
of  January  loth  and  25th  and  February  25th,  of  1898,  three 
articles  in  which  are  given  the  results  of  a  great  number  of 
experiments  made  with  vertical  glass  tubes  in  which  circulation 
was  produced  by  the  ascension  of  air  bubbles.  In  the  conditions 
which  I  have  stated,  the  maximum  discharge  of  water  always 
took  place  when  the  volume  of  air  was  practically  equal  to  the 
volume  of  water.  M.  Bellens  found  only  about  10  per  cent, 
difference  between  the  results  of  theory  and  practice. 

"  As  I  have  stated  in  the  Bulletin  ties  Ingeiiieurs  Civils  de  France 
(of  April,  1897),  if  we  call  Q  the  maximum  weight  of  water — 
calculated  by  the  formula  I  have  given — which  a  tube  is  capable 
of  discharging  during  unit  of  time,  T  the  temperature  of  the 
steam,  and  Ns  the  total  number  of  caloric  units  received  by  the 
tube  during  the  same  unit  of  time,  there  will  be  a  serious  danger 
each  time  that 

Ns>  Q  (606-5— 0-695  T). 
"  This  shows  for  reversible  cycles,  that  is  to  say  for  the  majority 


THE  MODERN  STEAM  BOILER.  259 

of  boilers,  a  maximum  of  specific  working  beyond  which,  con- 
trary to  the  general  opinion,  things  no  more  adjust  themselves. 
The  specific  discharge  diminishes  ;  the  column  of  mixed  water 
and  steam  travels  slower  and  slower  ;  the  circulation  becomes 
pulsatory  ;  long  plug  bubbles  drive  the  water  completely  out  of 
the  heated  tube  through  both  ends  at  once  ;  and  finally  the  tube 
melts  and  bursts." 

It  is  to  be  remarked,  hoxvever,  that  M.  Chasseloup-Laubat's 
calculations  are  occupied  almost  entirely  with  boilers  composed 
of  small  water-tubes,  so  that  his  maximum  amount  of  circulation 
is  obtained  when  the  steam  bubbles  form  plugs  or  pistons  which 
occupy  the  full  section  of  the  water-tube,  but  do  not  extend 
along  the  tube  farther  than  to  allowT  of  a  rapid  succession  of 
alternate  water  plugs  of  the  same  dimensions. 

Larger  quantities  of  steam  do  not  increase  the  amount  of  water 
carried  along  through  the  tubes,  but,  on  the  contrary,  diminish 
it,  and  produce  the  action  described  by  Mr.  Thornycroft1  as 
incidental  to  ordinary  circulation. 

With  tubes  of  larger  diameter  the  formation  of  these  plugs 
would  not  readily,  if  at  all,  take  place,  and  hence  the  calcula- 
tions do  not  wholly  apply  to  them. 

Moreover,  the  speed  of  circulation  hitherto  attained  in  any 
water-tube  boiler  is  evidently  insufficient  for  complete  transmis- 
sion of  the  heat,  as  evaporative  results  prove.  It  is  only  in  a 
rare  experiment  that  the  results  obtained  in  Thornycroft  boilers 
have  been  surpassed,  and  these  results  show  a  velocity  of  circula- 
tion only  sufficient  for  an  evaporation  of  20  Ibs.  of  water  per 
square  foot  of  heating  surface  per  hour — at  any  rate,  in 
combination  with  the  velocity  then  given  to  the  gases.  The  same 
may  be  said  of  the  boilers  of  M.  Niclausse  and  M.  Normand, 
although  it  is  clear  from  his  papers  "  On  the  Economy  of  Fuel 
in  very  Fast  Vessels"  and  "  On  Water-tube  Boilers,"2  that  the 
latter  appreciated  to  some  extent  the  importance  of  rapid  motion. 
Either,  therefore,  the  velocity  attainable  by  natural  circulation  is 
insufficient,  or  the  circulation  is  not  constant  and  steady  enough 
for  the  best  result.  It  is  necessary  to  repeat  that  the  important 
question  is  not,  What  is  the  speed  actually  attained  in  any  indi- 
vidual boiler  ?  but  is,  What  is  the  best  speed  for  the  water  in  view 

1  Min.  Proc.  Inst.  C.  E.,  Vol.  xcix.,  p.  46. 

-  Trans.  Inst.  X.  A.,  Vol.  xxxvii.,  p.  169  ;  Vol.  xxxvi. 

K  2 


260  THE  PRACTICAL  PHYSICS  OF 

of  heat  transmission  ?  and  this  being  known,  what  are  the  best 
means,  consistent  with  the  other  elements  of  the  problem,  of 
producing  this  movement  ? 

Forced  Circulation. — It  seems  to  be  certain  that  mechanical 
means  must  be  introduced  in  order  to  ensure  a  greater  velocity 
of  circulation  and  a  more  constant  movement  of  the  water  than 
that  which  is  due  to  the  natural  action  of  boiling.  Under  such 
altered  circumstances,  of  course,  such  calculations  as  those  of 
M.  Chasseloup-Laubat  become  inapplicable.  Various  devices 
have  already  been  introduced  at  different  times  with  the  object 
of  securing  regularity  in  the  action  and  direction  of  the  circu- 
lating currents,  but  none  as  yet  for  the  purpose  of  obtaining 
greater  speed. 

Artificial  Circulation. — The  circulation  resulting  from  the  use 
of  these  devices  has  been  termed  artificial  circulation  in  contra- 
distinction to  that  which  is  due  to  the  natural  process  of  boiling, 
and  it  must  be  further  distinguished  clearly  from  forced  or 
accelerated  circulation  such  as  is  here  proposed. 

The  difference  between  these  methods  (i.e.,  natural  and  forced 
circulation)  has  already  been  emphasised  in  connection  with  the 
subject  of  heating  by  hot  water  by  Mr.  W.  Anderson,1  who 
remarked  :  "  When  the  water  circulates  through  the  pipes  by 
virtue  of  the  difference  of  temperature  of  the  flow  and  return 
currents  only,  it  is  impossible  to  count  on  a  greater  mean 
temperature  of  the  pipes  than  from  160°  to  180°.  When  forced 
circulation  is  adopted — as  when  the  water  is  propelled  by  a 
centrifugal  pump  and  is  under  a  pressure  of  about  70  feet — a 
much  higher  temperature  can  be  attained."  In  this  case  the 
increase  of  temperature  may  be  partly  clue  to  the  higher  pres- 
sure in  the  pipes,  but  the  improved  result  is  no  doubt  also  owing 
to  the  more  rapid  movement  of  the  water  produced  by  the 
pump. 

Mr.  J.  G.  Hudson  remarked  (in  the  Engineer,  Vol.  Ixx.,  p.  483) 
that — "  Heating  water  below  its  boiling  point  by  steam  is  in 
some  respects  a  parallel  case  to  what  takes  place  in  a  steam 
boiler.  In  each  there  is  on  one  side  of  the  surface  a  medium 
which,  under  normal  conditions,  transfers  heat  with  great 
reluctance  in  comparison  with  the  medium  on  the  opposite  side 
of  the  surface. 

1  Min.  Proc.  Inst.  C.  E.,  Vol.  xlviii.,  p.  257. 


THE  MODERN  STEAM  BOILER.  261 

"  In  the  steam-heating  apparatus  the  water  is  the  sluggish 
medium,  and  in  the  boiler  it  is  the  hot  gas.  These  resemble 
each  other  in  being  both  very  bad  transmitters  of  heat  by  any 
method  other  than  convection.  In  the  case  of  heating  water  by 
steam,  it  can  be  conclusively  shown  that,  other  things  being 
equal,  the  quantity  of  heat  taken  up  by  the  water  is  almost 
wholly  a  question  of  the  speed  with  which  the  latter  traverses 
the  heating  surface,  the  transmission  increasing  only  somewhat 
less  rapidly  than  the  speed.  So  important  is  this  influence  that 
the  transmission  has  been  found  to  vary  from  as  little  as  20  or 
30  units  per  degree,  where  the  water  was  confined  in  small  tubes 
and  moved  very  slowly,  up  to  nearly  1,000  units,  according  to 
the  speed." 

Amongst  the  more  important  devices  in  use*  in  connection 
with  artificial  circulation  are  the  automatic  feeds  of  Yarrow, 
Thornycroft,  Belleville,  and  perhaps  others,  the  automatic  valves 
of  Belleville  and  Solignac,  and  the  "  Emulseur  "  of  Dubiau.1 

The  same  result,  viz.,  the  regular  feeding  of  the  water  to  the 
evaporating  surface,  was  obtained  with  the  pumps  supplying 
those  boilers,  such  as  the  Boutigny,  Serpollet,  De  Laval,  Simpson 
and  Boclman,  and  others,  which  are  or  were  used  to  flash  small 
successive  quantities  of  water  wholly  into  steam  without  expend- 
ing heat  in  boiling  and  circulating  a  larger  quantity.  The  boiler 
introduced  by  Mr.  Benson  in  1856  also  had  artificial  or  "  mecha- 
nical circulation,"  as  it  was  then  called,  and  this  was  perhaps  the 
earliest  plan  in  which  all  the  water  in  circulation  in  a  boiler  was 
passed  through  a  pump.  There  was,  however,  no  thought  of  an 
increased  velocity  of  circulation  in  this  plan,  but  the  boiler  being 
composed  of  several  flattened  spirals,  as  in  the  Belleville  boiler 
of  to-day,  but  composed  of  horizontally  placed  tubes  of  small 
diameter,  the  mechanical  arrangement  \vas  adopted  to  ensure  a 
steady  movement  of  water  throughout  the  whole  length  of  the 
spirals,  so  that  the  tubes  should  not  be  burned,  in  consequence 
of  shortness  of  water  in  some  parts. 

Forced  Circulation. — There  should  evidently  be  a  development 
of  this  system  carried  out,  by  which,  not  only  will  all  the  water 
in  the  boiler  be  circulated  by  means  of  a  pump,  but  also  the 
water  will  be  propelled  through  the  boiler  passages,  or  over  the 

1  See  note  Sur  les  Chaudieres  a  Emulsion  cle  Vapeur,  par  M.  M.  Jouffret, 
Mem.  et  Comp.  Rend,  de  la  Soc.  des  Ingenrs.  Civils,  January  7,  1898,  p.  79. 


262 


THE  PRACTICAL  PHYSICS  OF 


heating  surface,  at  a  greater  speed  than 
that  which  is  due  to  the  natural  action 
of  boiling.  The  expenditure  of .  power 
required  for  this  operation  will  be 
trifling,  because  the  same  pressure  being 
on  both  sides  of  the  pump,  the  power 
required  will  be  regulated  simply  by 
the  quantity  of  water  set  in  motion, 
its  speed,  and  the  height  to  which  it 
is  forced — some  allowance  being,  of 
course,  made  for  loss  of  power  by 
friction. 

In  addition  to  the  control  of  speed 
of  the  movement  of  wrater  over  the 
heating  surface  which  this  method  gives, 
it  also  gives  control  of  the  direction  in 
which  the  water  is  caused  to  flow. 
The  results  obtained  with  "  film " 
evaporating  vessels  show  how  important 
this  may  be. 

Film  Evaporating  System. — This  system 
of  evaporating  has  been  tried  in  various 
forms,  and  carried  to  a  very  successful 
issue  in  the  apparatus  of  M.T.  James 
Foster,1  who  makes  use  of  the  form 
of  tube  shown  in  Fig.  122.  The 
top  of  each  tube  is  fitted  with  a  liquor 
spreader  or  distributor  chamber  with 
bayonet  catch  attachment  to  the  tube. 
This  chamber  has  three  legs  or  ribs 
with  open  spaces  between,  these  legs 
resting  on  the  top  tube  plate  and,  the 
film  tube  being  suspended  from  them. 
The  liquor  to  be  concentrated  or  boiled 
is  fed  into  these  chambers  and  runs 
down  the  annular  openings  in  each  KIG  I22 

of  the  three  legs  or  ribs.  It  is  then 
distributed  or  directed  by  the  shields  and  runs  down  the  inner 


luOn  Evaporation  by  the   Multiple  System,"  also  Trans.  Inst.  E.  and  S., 
Vol.  xli  ,  p. 141. 


THE  MODERN  STEAM  BOILER.  263 

surface  of  the  heating  tube  in  a  thin  film  or  layer.  The 
annular  spaces  between  the  shields  and  the  heating  tube  are 
made  larger  at  the  top  than  at  the  lower  end,  because  the 
quantity  of  liquid  becomes  smaller  on  account  of  evaporation 
as  it  descends.  Each  film  tube  of  the  usual  length  is  fitted 
with  five  distributing  shields,  and  as  the  liquid  evaporates  the 
vapour  passes  under  these  shields,  through  the  openings  in  the 
film  tube  which  are  there,  and  up  through  the  centre  of  the 
film  tube  to  "the  top  chamber.  By  such  means  the  vapour  can 
escape  as  it  is  formed  and  without  priming  water,  whilst 
the  whole  surface  of  the  heating  tube  is  covered  with  liquid, 
which  does  not  run  down  in  rivulets.  The  usual  length  of  these 
working  tubes  has  been  (in  evaporating  vessels)  4  ft.  2  in.  over 
the  tube  plates,  and  i-J  in.  internal  diameter,  the  film  tube 
being  placed  inside  of  each  heating  tube.  Although  in  these 
evaporating  vessels  steam  is  used  as  the  heating  medium,  yet 
there  is  no  danger  of  the  heating  tube  being  burned  when 
exposed  to  the  higher  temperature  due  to  the  hot  gases  from 
a  fire.  Not  only  is  ordinary  evaporation  sufficient  to  prevent  such 
overheating,  but  further,  a  result  noted  in  Miss  Bryant's 
experiments  (see  Chap.  IV.,  p.  185)  shows  that  with  a  thin  film  of 
liquid  the  evaporation  is  quickened  and  the  temperature  of  the 
metal  heating  surface  is  lowered  even  beyond  the  temperature 
found  in  the  same  surface  when  a  larger  quantity  of  water  is  present. 

For  an  adaptation  of  the  film-tube  system  to  boilers,  it  is 
necessary  to  have  forced  circulation,  because  the  water  has  to  be 
continuously  supplied  to  the  main  chamber  at  the  top  of  the 
heating  tubes,  from  which  it  enters  the  various  distributor 
chambers  of  the  tubes.  The  film  tube  is  extended  up  to  an 
upper  division  of  the  main  top  chamber,  which  is  thus  filled 
only  with  steam. 

With  forced  circulation  it  is  possible  to  ensure  that  the 
currents  of  water  and  hot  gases  travel  in  opposite  directions, 
and  although  it  is  possible  also  to  arrange  this  with  natural 
circulation,  yet  the  limit  of  velocity  of  movement  is  soon  reached 
with  that  plan.  In  no  other  way  can  the  velocity  of  circulation 
be  controlled  and  the  direction  and  quantity  maintained  steadily, 
than  by  the  use  of  mechanical  appliances  for  circulation  of  the 
water,  just  as  they  have  been  found  necessary  for  proper  control 
of  the  combustion  and  gases. 


264  THE  PRACTICAL  PHYSICS  OF 

Critical  Velocity. — A  much  less  speed  is  required  for  water, 
however,  than  is  necessary  where  air  'or  gases  have  to  be  moved 
either  for  rapid  combustion  or  heat  transmission.1  Professor 
Osborne  Reynolds  *  has  shown  that  it  is  only  at  low  velocities 
and  when  unaffected  by  changes  of  temperature  that  water  flowrs 
in  straight  stream  lines  parallel  with  the  axis  of  the  pipe.  What 
he  has  called  the  "  critical "  velocity  for  any  pipe,  or  the 
point  at  which  the  water  ceases  to  flow  in  straight  stream  lines, 
is  given  by  the  expression :  — 

v  =  -L? 

278  D 

where  D  =  the  diameter  of  the  pipe  in  metres, 
T  =  the  temperature  of  the  water, 
P  =  (I  +  -0336T  +  -00022IT2)-1 
Vc  =  the  critical  velocity  in  metres  per  second. 

Mr.  Stanton3  observed  that  in  a  pipe  of  1-39  centimetres 
diameter  the  critical  velocity  in  centimetres  per  second  was 
found  at  about  28*6  as  maximum. 

The  results  of  Mr.  Stanton's  experiments  showed  that  the  heat 
transmitted  from  metal  (copper)  to  water  was  nearly  propor- 
tional to  the  velocity  of  the  water  ;  but  these  experiments  were 
carried  out  with  small  pipes  and  with  small  temperature  differ- 
ences, and  hence  do  not  afford  very  certain  information  for  our 
special  subject.  The  highest  velocity  experimented  with  seems 
to  have  been  186  centimetres  per  second,  but  in  those  on  the 
effect  of  variation  of  velocity,  the  values  of  v  used  were  69,  98, 
and  123-2  centimetres. 

There  are  several  collateral  actions  connected  with  the  circu- 
lation of  water  in  boilers,  upon  which  forced  or  mechanical 
circulation  must  exert  a  very  decided  influence.  These  are 
priming,  delayed  ebullition,  and  the  heating  of  the  feed  water. 

Priming. — As  to  priming,  whatever  may  be  the  special  condi- 
tions of  the  water,  or  of  the  boiler  surfaces,  which  favour  frothing 
of  the  water,  there  is  no  doubt  that  the  boilers  which,  from  their 
design,  cause  the  projection  of  considerable  quantities  of  water 

1  See  Chap.  IV.  more  fully  on  this  point. 

?  Phil.  Trans.,  1884,  pp.  935-982. 

3  Phil.  Trans.,  A.,  1897,  Vol.  cxc.,  pp.  67-88. 


THE  MODERN  STEAM  BOILER.  265 

into  the  steam  space,  must  be  very  liable  to  the  presence  of 
priming  water  in  the  steam  which  they  deliver.  Consequently 
if  we  could  by  suitable  arrangements  diminish  this  action,  the 
chances  of  obtaining  dry  steam  would  be  greatly  increased. 
The  use  of  forced  circulation,  combined  with  causing  the 
currents  of  water  and  of  hot  gases  to  travel  in  opposite  direc- 
tions, for  the  carrying  out  of  which  it  furnishes  the  means, 
attains  the  desired  end  by  ensuring  that  the  formation  of  steam 
takes  place  when  it  can  escape  at  once  into  the  steam  space, 
encumbered  by  only  the  minimum  of  water.  In  boilers  which 
have  an  upward  current  of  water  in  the  tubes,  the  maximum 
amount  of  steam  formation  takes  place  at  their  upper  ends,  so 
that  the  steam  does  not,  as  in  other  boilers,  force  along  with  it  a 
large  volume  of  water  up  through  the  whole  length  of  the  tubes. 
In  the  boilers  arranged  for  a  downward  current  of  water  the 
method  of  exposing  the  water  to  heat  in  films  makes  it  certain 
that  the  steam  can  escape  at  once  without  carrying  a  large 
quantity  of  water  with  it.  Nevertheless,  the  point  at  which 
saturated  steam  becomes  perfectly  dry  and  enters  the  condition 
of  steam  gas  is  difficult  to  reach,  so  that  it  is  more  than  likely 
that  all  steam  not  actually  superheated  by  direct  transmission  of 
heat  carries  with  it  more  or  less  vapour  in  a  finely  attenuated  con- 
dition. Some  experiments  by  Professor  Osborne  Reynolds1  with 
a  "  wire-drawing  calorimeter  "  apparently  prove  this  and  raise  a 
doubt  as  to  whether  the  steam  tables  calculated  from  Regnault's 
experiments,  made  presumably  with  dry  saturated  steam,  are 
correct.  The  wire-drawing  calorimeter  is  one  form  of  ingenious 
apparatus  which  has  been  devised  for  obtaining  a  measure  of  the 
percentage  of  moisture  in  steam.  Since  the  methods  proposed 
by  Hirn  and  Joule,  in  wrhich  the  steam  was  weighed,  either 
separately  or  mixed  with  a  known  weight  of  water,  various  steam 
calorimeters  have  been  devised  and  are  used  in  all  steam  boiler 
trials  which  are  carried  to  any  notable  degree  of  accuracy.  Of 
these  the  principal  instruments  are  those  of  Barrus,  Carpenter, 
Rateau  and  Peabody.2 


1  On  "  The  Dryness  of  Steam,"  etc.    Manchester  Literary  and  Philos.  Soc., 
1896. 

-  See  Professor  Unwin  on  "  Determining  the  Dryness  of  Steam,"  Brit.  Assoc. 
Reports,  and  Proc.  Inst.  Mech.  Eng.,  January,  1895. 


266  THE  PRACTICAL  PHYSICS  OF 

Delayed  Ebullition. — The  phenomena  of  delayed  ebullition  and 
of  superheating  the  water  in  steam  boilers,  although  rare,  are 
recognised  as  of  possible  occurrence  with  water  from  which  the 
air  has  been  removed  by  boiling,  and  which  is  also  free  from 
floating  or  other  impurities.1  But  as  almost  entire  quiescence  is 
a  necessary  condition  to  the  production  of  the  phenomena,  it  is 
apparent  that  the  continued  movement  of  the  water  by  mechanical 
means  must  prevent  any  such  actions  taking  place. 

Heating  Feed-Water. — Heating  the  feed-water  is  also  made  the 
more  certain  and  easy  by  forced  circulation,  whether  the  feed- 
heaters  are  arranged  to  work  \vith  the  waste  heat  from  furnace 
gases,  or,  as  many  prefer,  to  be  heated  by  steam  taken  from  the 
exhaust  or  from  some  other  point. 

There  are  in  fact  four  different  methods  of  heating  the  feed- 
water,  viz.,  (i)  heating  by  the  waste  gases  from  the  furnace,  as  in 
Green's  and  other  "  Economisers "  on  land  ;  Mr.  E.  Kemp's 
"  Compound  boiler  "  (referred  to  in  Chap.  IV.),  the  Belleville, 
Yarrow  and  other  arrangements  for  marine  boilers  ;  (2)  heating 
by  exhaust  steam,  common  to  all  old  forms  of  injection  conden- 
sers and  now  used  for  feed-heating  alone  in  the  forms  used  by 
Bailey,  Wheeler,  Babcock  and  Wilcox  and  others  ;  (3)  heating 
by  steam  after  it  has  been  partially  used  or  expanded,  as  in  such 
arrangements  as  Weir's,  and  others  ;  and  (4)  heating  by  "  live  " 
steam,  as  in  the  feed-heaters  of  Caird  and  Rayner,  Babcock  and 
Wilcox,  Kirkaldy,  Row  and  others.  There  is  also  another  plan, 
that  of  Morrison's  feed-water  heater,  in  which  steam  from  an 
evaporator  is  admitted  to  and  condenses  amongst  the  feed- 
water.  This  is  apparently  an  indirect  method  of  utilising  the 
heat  of  live  steam.  The  live  steam  is  used  first*  to  evaporate 
sea  wrater,  and  some  of  the  heat  is  recovered  from  the  steam 
thus  formed  and  is  transmitted  to  the  feed- water. 

It  is,  of  course,  plain  that  the  utilisation  of  heat  which  would 
otherwise  go  to  waste,  as  in  plans  i  and  2,  must  be  an  economy  ; 
but  economy  has  also  resulted  from  the  use  of  plans  3  and  4, 
although  the  source  of  it  does  not  lie  so  distinctly  on  the  surface. 
There  seems,  however,  little  reason  to  doubt  that  the  explanation 


1  See  the  Engineer,  November  26th,  1875,  pp.  377-378  ;  Prof.  K.  H.Thurston, 
"  Manual  of  Boilers,"  pp.  268,  269  ;  Hirsch,  "  Annalesdes  Mines,"  Vol.  v.,  p.  171. 


THE  MODERN  STEAM  BOILER.  267 

of  the  improved  results  obtained  with  these  classes  of  feed- 
heaters  is  to  be  found  in  the  fact  that  an  increased  speed  of 
circulation  of  water  in  the  boiler  has  resulted  from  their  use,1 
causing  the  transmission  of  heat  from  the  hot  gases  to  be  carried 
farther  than  would  otherwise  have  been  the  case.  If  so,  this  is 
an  additional  argument  in  favour  of  forced  or  accelerated 
circulation. 

Conditions  to  be  Reached. — In  the  discussion  of  a  paper  on 
"Water-tube  Boilers"  by  Mr.  George  Halliday,  Wh.  Sch.  in 
Trans.  lust.  Marine  Engineers  (April  and  May,  1898),  Vol.  x., 
p.  76,  the  author  of  this  work  observed  that  "  the  best  results 
will  probably  be  reached  in  the  future  when  we  have  ascertained 
the  best  rates  of  movement  of  the  water  on  the  one  side  and  of 
the  lire  gases  on  the  other,  for  given  differences  of  temperature. 
Means  will  have  to  be  introduced  also  for  eliminating  the  various 
losses  or  uncertainties  which  belong  to  the  combustion  depart- 
ment of  the  boiler  as  at  present  arranged.  And  it  is  probable 
that,  in  order  to  obtain  the  best  results  in  this  department,  a 
distinct  development  of  combustion  under  high  pressure  will  be 
found  necessary.  All  this  may  issue  in  the  production  of  a 
completely  new  type  of  boiler." 

In  the  following  June,  Professor  Perry,  when  discussing  Mr. 
Halliday's  paper  on  "  Transmission  of  Heat  through  Plates  from 
Hot  Gases  to  Water"  (Trans.  Inst.  Engineers  and  Shipbuilders 
in  Scotland,  Vol.  xlii.,  p.  52),  expressed  a  similar  opinion.  He 
said,  "  One  small  tube  conveying  hot  gases,  dragged  through  at 
an  enormous  velocity,  and  concentric  tube  conveying  water  in 
the  opposite  direction  at  great  velocity.  They  had  in  that 
combination  a  method  of  giving  up  heat  which  was  fifty  times  as 
great  as  what  occurred  in  an  equal  amount  of  heating  surface  in 
the  best  existing  boilers.  That  led  to  the  result  that  the  boiler 
of  the  future  would  burn  its  fuel  under  pressure  in  a  very  non- 
conducting chamber,  and  the  products  of  complete  combustion 
would  pass  with  great  velocity  through  very  fine,  very  thin  tubes 
surrounded  with  water,  which  was  made  to  circulate  with  great 
rapidity  driven  by  a  pump  or  injector." 

In  the  main  these  views  agree,   though  it  is  probable  that 


1  See  the  Mechanical  Engineer,  Vol.  i.,  pp.  424-246  ;  vol.  ii.  pp.  784-786. 


268  THE  PRACTICAL  PHYSICS  OF 

Professor  Perry's  arrangement  of  gases  inside  and  water  outside 
will  not  give  so  good  a  result  as  the  reverse  of  that  arrangement 
should  give.  The  gases  must  pass  over  the  heating  surface  in 
enormously  larger  volume  than  the  water  ;  and  as  they  must 
necessarily  escape  at  a  comparatively  high  temperature,  it  is 
evident  that  they  should  form  the  atmosphere  which  envelops 
the  water-tube,  so  that  no  heat  can  be  radiated  away  from  the  hot 
water  surface.  But  both  are  agreed  in  the  conclusion  that  the 
water  should  be  circulated  by  mechanical  means  over  the  surface 
.in  process  of  its  being  caused  to  receive  heat  transmitted  from  the 
gases,  and,  moreover,  that  the  currents  of  water  and  of  gas  should 
be  made  to  travel  in  opposite  directions. 

Since  the  foregoing  chapter  was  written  some  experiments 
have  been  carried  out  by  Mr.  G.  Halliday  on  the  influence 
of  velocity  on  evaporation  in  tubes,  the  results  of  which  are 
interesting  and  apparently  contradictory,  though  the  experi- 
ments are  a  long  way  from  being  exhaustive  enough  to  warrant 
a  general  conclusion  being  drawn  from  them. 

The  first  set  of  experiments  was  published  in  the  Engineer  on 
1 2th  May,  1899,  and  the  second  set  on  29th  December,  1899, 
both  having  been  first  communicated  to  the  Institute  of  Marine 
Engineers1.  The  first  experiments  showed  that  up  to  a  certain 
point,  when  the  source  of  heat  was  kept  constant,  and  the 
difference  in  temperature  between  the  out-flowing  hot  and 
the  in-flowing  cold  water  was  about  150°  Faht.,  the  number 
of  thermal  units  absorbed  by  the  water  per  minute  increased 
steadily  with  the  speed  of  flow.  This  effect  was  not  much 
altered  when  the  water  was  heated  up  to  boiling  point,  but 
the  rate  of  absorption  was  less  at  boiling  point  than  at  10  degrees 
below  it. 

The  apparatus  then  used  consisted  of  a  vertical  glass  tube 
with  a  spiral  tube  of  small  diameter  placed  inside  of  it  and 
sealed  into  it  at  each  end.  Water  from  a  cistern  was  allowed  to 
flow  through  the  spiral  from  below,  passing  a  thermometer 
placed  at  each  end  of  the  spiral,  and  flowing  from  the  top 
end  into  a  graduated  measure.  The  space  surrounding  the 


1    See  Trans.  Inst.  Marine  Engineers,  Vol.  xi.,  84th  paper;  also  "Science 
Abstracts,"  Vol.  for  1900,  pp.  267-268. 


THE  MODERN  STEAM  BOILER.  269 

spiral  was  kept  full  of  steam  at  atmospheric  pressure,  super- 
heated by  being  passed  through  a  copper  coil  heated  in  a 
Bunsen  flame.  With  this  apparatus  there  seemed  to  be  a 
critical  point  in  the  velocity  beyond  which  the  thermal 
absorption  fell  away,  sometimes  very  rapidly.  That,  however, 
was  due  to  the  heating  powers  of  the  apparatus  being  too 
limited  to  cope  with  the  requirements  of  the  water  at  the  higher 
velocities  employed. 

In  the  later  experiments  the  water,  previously  heated  to 
boiling  point  in  a  tank  or  cistern,  was  made  to  flow  upwards 
through  a  vertical  copper  tube,  heated  throughout  its  entire 
length  by  a  Fletcher  gas  burner.  The  mixture  of  steam 
and  water  delivered  from  this  copper  tube  was  passed  into 
a  separator,  from  which  the  wrater  went  to  a  measuring  flask, 
and  the  steam  through  a  condenser  to  a  graduated  measure  for 
the  condensed  steam.  The  experiments  made  with  this  form  of 
apparatus  were  undertaken  to  test  the  rate  of  heat  transmission 
with  water  which  is  freely  giving  off  steam,  and  is  also  made  to 
flow  through  the  heating  tube  at  different  velocities,  the 
effects  of  the  presence  of  steam  not  having  been  studied  in 
the  former  experiments. 

Mr.  Halliday  stated  that  there  appeared  to  be  a  maximum  rate 
of  evaporation  at  a  certain  speed  of  the  water,  and  that  on  either 
side  of  that  point  the  evaporation  diminished,  a  velocity  which 
gave  an  evaporation  about  equal  to  the  quantity  not  evaporated, 
i.e.,  an  evaporation  of  half  the  quantity  of  water  passing  in 
a  given  time,  seemed  to  give  the  best  result.  This  result 
was  independent  of  the  degree  of  heat  applied  within  the  limits 
of  the  apparatus  used,  the  curves  of  results  with  higher  heats 
having  the  same  form  as  those  of  lower  heats,  but  appearing  at  a 
higher  level  in  the  diagram. 

He  concluded  from  these  experiments  that  whilst  the  quantity 
of  water  evaporated  depends  on  the  quantity  of  heat  supplied  to 
the  tube,  and  on  the  velocity  of  the  water  through  the  tube,  yet 
the  greater  the  speed  of  water  through  the  tubes  of  a  water-tube 
boiler,  beyond  a  certain  point,  the  less  will  be  the  evaporation. 
This,  however,  does  not  necessarily  follow,  because  Mr. 
Halliday's  experiments  were  too  limited  in  extent  to  permit 
of  any  such  general  deduction  being  properly  derived  from 


270  THE  PRACTICAL  PHYSICS  OF 

them.  Both  the  range  of  temperatures  and  the  velocity  of 
circulation  employed  by  him  were  restricted,  and  the  conditions 
of  the  application  of  heat  to  the  tube,  and  of  the  movement 
of  the  water  in  it,  were  such  that  no  sound  conclusion  can 
be  drawn  from  these  experiments  which  would  be  applicable  to 
a  different  set  of  conditions. 


CHAPTER   VI. 

THE  INFLUENCE  OF  TEMPERATURE  ON  TENACITY  AND 
DUCTILITY. 

IT  would  appear  that  a  limit  to  the  heating  of  boilers,  and  to 
the  pressure  and  temperature  of  steam  carried  in  them,  is  fixed 
by  the  effects  of  elevation  of  temperature  upon  the  tenacity  and 
ductility  of  iron  and  steel — as  well  as  other  metals. 

Although,  in  some  of  the  experiments  on  heat  transmission 
mentioned  in  Chapter  IV.,  the  metal  plate,  or  bottom  of  the  open 
apparatus  in  which  water  was  evaporated,  reached  a  red-heat, 
yet  it  is  certain  that  in  a  vessel  subject  to  steam  pressure,  such 
results  could  not  have  been  attained,  or,  at  any  rate,  would  have 
been  accompanied  by  some  danger  of  explosion  or  collapse. 

The  investigation  of  the  subject  in  a  practical  way  dates  from 
Sir  W.  (then  Mr.)  Fairbairn's  l  researches,  although  some  experi- 
ments on  the  ultimate  tenacity  of  iron  at  high  temperatures  had 
been  previously  made  by  Baudrimont,2  Seguin,  and  by  the  Franklin 
Institute.  These  earlier  experiments  \vere  conducted  on  a  small 
scale,  without  reference  to  the  temporary  or  permanent  elongations 
of  the  material,  or  to  the  effect  of  heat  on  its  elasticity  and  ductility. 

Fairbaim's  Investigations. — Mr.  Fairbairn  observed  no  effect 
on  the  strength  of  plate  iron  up  to  almost  400°  F.  At  a  "scarcely 
red  "  heat,  the  breaking  weight  of  plates  was  reduced  to  16-978 
tons  from  21  tons  at  60°  F.  ;  whilst  at  a  "  dull-red  "  it  was 
further  reduced  to  13-621  tons. 

Messieurs  Tremery  and  P.  Saint  Brice,3  aided  by  the  cele- 
brated Cagniard  Latour,  found  that  at  nominally  the  same 
temperature  (rouge  sombre)  a  bar  of  iron  was  reduced  in  strength 
to  one-sixth  of  its  strength  when  cold.  Although  this  was  a 
greater  reduction  of  strength  than  Fairbairn  observed,  yet  it  must 
be  remembered  that,  for  want  of  reliable  means  of  measuring 

1  On   the   Tensile    Strength   of     Wrought    Iron    at   Various   Temperature 
Reports.     British  Association,  1856,  p.  405. 
-  Annales  de  Chimie  et  de  Physique,  3rd  ser.  30,  p.  304  (1850). 
3  Annales  des  Mines,  2nd  series,  Vol.  iii.,  p.  513. 

271 


272  THE  PRACTICAL  PHYSICS  OF 

high  temperatures  in  these  clays,  the  estimation  of  such  tempera- 
tures was,  to  a  great  extent,  done  by  the  eye,  and  a  variation  in 
the  amount  of  daylight  would  cause  an  apparent  difference  in 
the  colour  observed  and  therefore  in  the  temperature  estimated. 
"  Fairbairn's  data  would  show  that  the  ultimate  strength  of 
wrought  iron,  is  reduced  to  about  one-half,  but  M.  Tremery's 
result  explains  the  generally  instantaneous  collapse  of  flues  when 
made  red-hot,"  although  their  factor  of  safety  may  originally 
have  been  six. 

"  A  most  important  question,"  wrote  Mr.  F.  A.  Paget  in  1865, 
"  is  the  effect  of  temperatures,  whether  high  or  low,  on  the 
elasticity  of  the  material — whether  iron  will  take  a  permanent 
set  with  greater  facility  at  a  high  temperature.  These  data  are 
really  more  important  than  those  on  the  ultimate  strength,  as 
they  would  show  the  influence  of  temperature  on  the  elastic 
limit.  Here  again  is  a  vacancy  in  existing  knowledge,  which 
can  scarcely  be  said  to  be  filled  up  by  the  few  experiments  of  the 
late  M.  Wertheim1  on  very  small  wires. 

"  Wertheim1  s  Experiment, — He  found,  however,  that  the  elasticity 
of  small  steel  and  iron  wire  increases  from  15°  C.  to  100°  C.,  but 
at  200°  it  is  not  merely  less  than  at  100°,  but  sometimes  even  less 
than  at  the  ordinary  temperature. 

"  As  Wertheim  used  in  his  experiments  wire  which  according 
to  his  statement  had  a  diameter  of  only  from  0*1  to  o-5  line,  he 
was  but  little  exposed  to  error  in  respect  of  its  curvature  ;  but 
on  the  other  hand,  he  was  unable  accurately  to  measure  its  sec- 
tional area,  except  by  calculating  the  mean  area  from  the  specific 
gravity.  As  the  wires  were  only  about  2-5  feet  long  between 
the  points  where  the  elastic  elongations  were  measured,  and -as 
these  measurements  were  obtained  by  means  of  a  cathetometer, 
the  values  of  the  modulus  of  elasticity  calculated  by  him  from 
his  experiments  on  traction  not  (infrequently  varied  for  the  same 
iron  and  steel  wire  to  the  extent  of  10  per  cent,  and  upwards. 

"  The  modulus  of  elasticity  may  certainly  be  more  accurately 
obtained  by  flexion  than  by  traction,  as  the  amount  of  deflection 
may  be  considerably  greater,  and  therefore  more  accurately 
measured  than  the  elastic  elongation  by  tension.  But  supposing 
that  the  value  of  the  modulus  of  elasticity  thus  obtained  is  an 

1  Comptes  Rendus,  Vol.  xix.,  p.  231. 


THE  MODERN  STEAM  BOILER.  273 

exact  measure  of  the  elastic  force  on  stretching,  it  is  assumed 
that  this  force  is  equal  to  the  elastic  force  on  compression,  whilst, 
according  to  Hodgkinson,  the  latter  for  iron  is  about  f  of  the 
former  ;  and,  also,  that  by  different  strains  in  different  directions, 
and  by  the  change  of  form  in  the  sectional  area  which  occurs  on 
flexure,  other  forces  are  developed  or  the  conditions  are  other- 
wise so  changed  that  the  calculations  on  the  common  formula 
become,  as  some  authors  affirm,  uncertain.  •  Wertheim  in  one  case 
obtained  the  modulus  of  elasticity  for  steel  wire  more  than  20  per 
cent,  higher  by  means  of  transverse  vibration  than  by  traction. 

Kupffers  Experiments. — tl  Kupffer's J  determinations  of  the 
modulus  of  elasticity  by  flexion  and  transverse  vibrations  agree 
very  well  among  themselves;  but  although  the  amount  of  deflec- 
tion was  determined  in  his  experiments  with  great  accuracy  by 
affixing  mirrors  to  the  ends  of  the  sample-bars  and  measuring 
the  inclination  which  these  mirrors  assumed  in  different 
positions  of  the  bars,  yet  his  results  may  be  affected  by  errors 
amounting  to  at  least  i^  per  cent.,  as  his  bars  had  a  thickness  of 
only  0*8  to  17  line.  The  third  power  of  this  thickness  enters 
into  the  formula  for  calculating  the  modulus  of  elasticity  by 
flexion,  and  therefore  an  error  in  measurement  of  0*00058  inch, 
which  for  the  thinner  bars  is  more  than  ^  per  cent,  of  their 
thickness,  causes  an  error  of  upwrards  of  i^  per  cent,  in  the 
modulus.  That  an  error  of  measurement  of  this  magnitude  was 
committed  may  be  seen  by  comparing  the  thickness  measured 
with  that  calculated  from  the  specific  gravity." 

"  There  is  another  very  important  point  with  respect  to  wrought 
iron  which  has  scarcely  received  the  attention  it  deserves.  As 
would  appear  from  a  number  of  phenomena,  there  seems  to  be 
a  sort  of  thermal  elastic  limit  with  iron.  When  heated,  and 
when  its  consequent  dilatation  of  volume  does  not  exceed  that 
which  corresponds  to  (perhaps)  boiling  point,  it  returns  to  its 
original  dimensions.  Beyond  a  certain  temperature  it  does  not 
contract  again  to  its  pristine  volume,  but  takes  a  permanent  dila- 
tation in  consequence,  apparently,  of  its  elastic  limits  having 
been  exceeded.  A  number  of  observers  have  determined  the 
fact  with  cast  iron,  and  though  wrought  iron  has  not  been 
expressly  investigated  in  this  direction,  there  is  no  doubt  that  it 

1  Recherches  Experimentales  sur  1'elasticite  des  Metaux,  etc.,  par.  A.  J. 
Kupffer.  St.  Petersburg,  1850. 


274 


THE  PRACTICAL  PHYSICS  OF 


exhibits  a  similar  behaviour.  Thus,1  a  number  of  years  ago  an 
Austrian  engineer,  named  C.  Kolm,  remarked  that  a  boiler  about 
12  metres  long  and  1-57  metre  in  diameter,  with  a  thickness  of 
plate  of  o'on,  permanently  expanded  at  a  temperature  corre- 
sponding to  a  steam  pressure  of  5  atmospheres  (153°  C.)  by 
0-07193,  and  did  not,  when  cold,  return  to  its  original  dimen- 
sions. The  same  thing  has  been  noticed,  by  means  of  very 
accurate  measurements,  with  other  boilers. 

"  A  number  of  experiments  by  Lieut.-Col.  H.  Clerk,2  of  Wool- 
wich, on  wrought-iron  cylinders  and  plates,  bear  distinct  evidence 
of  a  dilatation  of  volume  in  wrought  iron  when  repeatedly  heated 
and  suddenly  cooled." 

These  facts  show  that  such  tests  or  experiments  as  those 
described  by  the  late  Mr.  W.  Parker3  (in  Trans.  Inst.  N.  A.,  Vol. 
xxvi.,  p.  253)  and  by  Mr.  John  Scott,  C.B.  (ibid.,  Vol.  xxx., 
p.  285),  must  be  incomplete  as  showing  what  precise  strains 
iron  or  steel  is  subject  to  under  conditions  of  actual  work. 

A  considerable  amount  of  research  has  been  carried  out  in 
some  of  these  directions  since  the  date  of  Mr.  Paget's  paper, 
but  there  is  still  room  for  further  investigation  in  connection 
with  the  latter  questions  raised  by  him. 

Fairbairn's  Results. — Mr.  Fairbairn's  experimental  results  on 
the  tensile  strength  of  boiler  plate  and  of  rivet  iron  at  different 
temperatures  are  given  in  the  following  Tables  : — 

TABLE  LI. 


Breaking  Strains. 

Temperature 
in  degrees  Faht. 

In  the  direction  of  the  fibre. 

Across  the  fibre. 

Per  sq.  inch  in  Ibs. 

Per  sq.  inch  in  tons- 

Per  sq.  inch  in  Ibs 

Per  sq.  in.  in  tons. 

0 

49,009 

21-88 

60 

50,219 

22-4I 

41,881 

18-69 

114 

41,356 

1846 

44,160 

19-71 

212 

44,717 

19-96 

45,680 

20-39 

270 

44,020 

19-65 



340 

49,968 

22-31 

42,088 

18-79 

395 

46,086 

20-57 

Red  heat 





34,272 

i5'30 

1  Percy's  "  Metallurgy,"  Vol.  Iron  and  Steel  (1864),  p.  872. 

2  Proceedings  of  the  Royal  Society,  March  5,  1863. 

3  See  also  Trans.  Inst.  N.  A.,  Vol.  xix.,  pp.  178,  179. 


THE  MODERN  STEAM  BOILER. 


275 


In  the  above  instances  the  plates  experimented  on  were 
Staffordshire  wrought-iron  boiler  plates  of  ordinary  quality. 
In  the  following  Table  are  results  of  experiments  on  the  tensile 
strength  of  rivet  or  bar  iron  at  a  greater  range  of  temperature 
than  the  above. 

TABLE  LI  I. 


Temperature  in  degrees  Faht. 

Mean  Breaking  Weight. 

Per  square  inch,  in  Ibs. 

Per  square  inch,  in  tons. 

-30 

63,239 

28-26 

60 

62,8l6 

28-05 

114 

70,845 

3I'6l 

212 

79,271 

35-39 

250  to  270 

82,636 

36-89 

310  to  325 

84,046 

37-52 

415  to  435 

83,943 

37-47 

Red  heat. 

35,ooo 

15-62 

"  The  maximum  strength  of  rivet  iron  appears  to  be  attained 
at  a  temperature  of  320°  F.  This  is  above  the  temperature  at 
which  the  maximum  strength  of  plates  was  attained,  but  little  or 
no  alteration  of  strength  is  observable  in  plates,  whilst  that  of 
bars  is  increased  nearly  one-half.  The  iron  was  of  good  quality, 
made  from  carefully  selected  scrap  iron." 

-Knnt  Sty ff^s  Results. — Very  careful  and  complete  experiments 
on  tensile  strength  and  elasticity  at  different  temperatures  were 
carried  out  with  both  iron  and  steel  by  Professor  Knut  Styffe, 
Director  of  the  Royal  Technological  Institute  at  Stockholm,  and 
an  excellent  translation  into  English  of  his  record  of  the  work 
was  made  by  Mr.  C.  P.  Sandberg.1  The  experiments  at  high 
temperature  were  carried  out  by  means  of  special  apparatus,  the 
heating  of  the  specimens  being  accomplished  by  the  use  of 
melted  paraffin,  to  temperatures  ranging  between  212°  and  392°  F. 

Fracture  at  High  and  Low  Temperatures. — The  results  of  all  his 
experiments  on  fracture  at  high  and  low  temperatures  are 
collected  in  the  following  Table,  regarding  which  Professor  Knut 
Styffe  remarked  : — 

1  The  Elasticity,  Extensibility,  and  Tensile  Strength  of  Iron  and  Steel.  By 
Knut  Styffe.  Translated  from  the  Swedish  by  C.  P.  Sandberg.  London  : 
John  Murray,  Albemarle  Street.  1869. 


THE  PRACTICAL  PHYSICS  OP" 


TABLE  LI  II.— RESULTS  of  EXPERIMENTS  on  the  TENSILE 

All  the  bars  tested  were  filed  in  the  middle  to  smaller 

Those  bars  preceded  by  a  bracket   j    were 


No.  of 
experi- 
ment. 

Description  of  Steel  or  Iron. 

Sample  bars. 

Section  of  the  bar 
vhere  it  was  not  filed. 

Mean  area 
of  the 

section 
where 
tiled. 

Carbon, 
per  cent. 

Phos- 
phorus. 

,,„, 

Diameter 
or 
side. 

per  cent. 

inches 

sq.  in. 

{: 

Bessemer  steel  from  Hogbo,  marked  ro            

1-14 

O'OlS 

Round 

0-465 

0-1115 

{    4' 

... 



— 

•• 

0-1252 
0-1261 

{! 

„                              „         marked  O"6 

0-68 



" 

" 

0-1135 
0-1203 

U 

Bessemer  iron  from  Hogbo,  marked  0-3 

033 

— 

Square 

0-348 

0-0543 
0-0811 

U 

n                              n                11 

•- 

— 

Round 

0-465 

0-1069 

0-1045 

•f  :1 

Bessemer  steel  from  Carlsdal,  marked  0-4           

0-42 

— 

Square 

M 

0-1883 
0-1883 

!M 

US 

Uchatius  steel  from  Wikmanshyttan,  hardness  No.  0-2 

1-78 

- 

Round 

0-1042 
0-1042 
0-1091 

f  16 

„                                    „                   hardness  No.  3... 

0-69 



" 

0-1014 
0-0968 

{18 
I  19 

Cast  steel  from  Krupp,  marked  with  one  crown 

0-62 

0'02 

" 

;; 

0-1209 
0-1261 

{20 
(21 

„ 

M 

n 

" 

,, 

0-1187 
0-1141 

{22 
I  23 

Puddled  steel  from  Surahammar,  marked  N.P.  i 

0-8 

— 

Square 

„ 

0-1956 
0-1957 

{24 

125 

,,                              ,,                  marked  N.H  i 

0-7 

— 

Round 

,, 

0-1233 
0-1195 

{26 

\27 

„                              ,,                  marked  B.2  

°"M 

— 

" 

0-1145 
0-1180 

{28 

(29 

marked  N.P.  3 

— 

— 

;; 

0-1252 
0-1203 

{30 
131 

English  pulled  from  Low  Moor                

0'2I 

0-068 

;; 

;; 

0-1348 
0-1380 

{32 
(33 

I  35 

{36 
I  37 



n 

» 

.- 

:- 

0-1348 
0-1241 

01952 
0-1234 

0-1256 
0-1343 



„ 

;; 

'• 



» 

i  Compare 
2  Xos.  3,  4,  7,  and  8  did  not  form  part  of  those  ordered 


THE  MODERN  STEAM  BOILER. 


277 


STRENGTH  of  Iron  ,\\i>Stu-l  at  DIKKERENT  TEMI'KR.VH-KFS 
dimensions  for  a  length  of  from  4  to  6  inches, 
originally  parts  of  the  same  bar. 


Breaking  weight  per 
sq.  inch  of  the 
original  mean  area 
of  the  filed  part 
of  llu-  bar. 

Area  of 
fracture. 

Ratio 
between 
he  area  ill 
Ji  .K  ture 
and  the 
original 

irea  of  the 
Tiled  part. 

Elongation  by 
rupture. 

Specific  gravity  determined 
after  the  experiment. 

Tempera- 
ture of 
the  bar 
during  the 
experi- 
ments. 

Fahr. 

The  bar 

broken  in 

Excluding 
the  inch 
where  the 
fracture 
ook  place. 

On  a 

length  of 
5-2  inches, 
the  place 
)!'  fracture 
ncl  tided,  i 

Of  the 

part  not 
filed. 

Of  the 

filed  part. 

Difference 
between 
the 
specific 
gravities. 

Ibs. 

tons. 

sq.  in. 

per  cent. 

per  cent. 
4-0 

4*3 

M0,945 
137,034 

62-92 

61-17 

0-1II5 
0-0747 

I'OO 

0-80 

4'0 

3'5 

7-8508 

7-8491 

Q-OOI7 

+  53 
+330 

Water. 
Paraffin. 

115.078 
I3',032 

51-37 

58-49 

0-0985 
0-II37 

0-79 
0-90 

4'0 

5-0 

5'i 

5'5 

— 

— 

— 

+  55 
+  356 

Air. 
Paraffin. 

126,044 
123,653 

56-27 
55-20 

0-0878 
0-0914 

0-77 
0-76 

7'0 
5'9 

8-8 
8-6 

— 

— 

— 

-  40 

+  59 

Alcohol. 
Water. 

66,286 
77,677 

29-59 
34-67 

0-0148 
00344 

0-27 
0-42 

5'5 

5'5 

94 
9-2 

— 

— 

— 

+  50 
+350 

Ditto. 
Paraffin. 

77,482 
76,422 

34-59 
34-11 

0-0313 
00389 

0-29 
o-37 

2-8 

6-4 

8-0 
10-3 

7-8804 

7-878I 

0-0023 

+  60 
+320 

Water. 
Paraffin 

7'W>r 
74,589 

34-37 
33-29 

0-1257 
0-1299 

0-67 
0-69 

19-3 
15-3 

2I"2 

IS'  I 

— 

— 

— 

+     5 
+  60 

Alcohol. 
Water. 

1  41,768 
1  U.«)i6 
138,818 

63-28 

59-3.? 
61-97 

0-1041 
0-1042 

0-1060 

I  -00 
I  -00 

9-97 

3-3 
3-1 
2-4 

37 
3'9 

— 



- 

-  29 

+  59 
+282 

Alcohol. 
Air. 
Paraffin. 

114,526 
116,173 

51-12 

51-86 

0-0705 
0-0747 

0-78 
0-77 

12-9 
7-5 

9'5 

7'843I 

7-8263 

0-0168 

+  53 
+302 

Water. 
Paraffin. 

93,666 

95,793 

41-81 
42-76 

0-0731 
0-0878 

0*56 

070 

77 

I  "00 

1  1  '5 

7^473 
7'8465 

7-8463 
7-8292 

O'OOIO 

0-0173 

-  23 

+  57 

Alcohol. 
Water. 

88 

42-63 
41-81 

0-0653 
0-0699 

o'55 
o'6i 

I2'2 

6-7 

I5-9 
iro 

7-8435 

7-8389 

0-0046 

—  20 
+  So 

Alcohol. 
Water. 

123,172 
118,300 

54-98 
52-81 

0-1875 

0-1656 

0-96 
0-85 

80 

IO'I 

"'5 

— 

— 

— 

-  29 

+  60 

Alcohol. 
Water. 

102,518 

45-76 
41-63 

0-0949 
0-1003 

0-77 
0-84 

127 
6-8 

15-0 

7-7783 
7-7830 

77361 
7-7600 

0-0422 
0-0230 

+  55 
+  300 

Ditto. 
Paraffin. 

95.7*4 

^.754 

4273 
43-06 

0-1003 
0-0896 

0-88 
076 

9'3 
9'7 

10-4 
III 

— 

— 

— 

-  13 

+  57 

Alcohol 
Water. 

73,492 
70,266 

3280 
3I-35 

0-0796 
0-0699 

0-63 
0-58 

17-6 
7-0 

21-3 
9'9 







+  59 
+  311 

Ditto. 
Paraffin. 

61,277 

5",474 

27-35 
25-21 

0-0666 
0-0654 

o-49 
0-47 

28-8 
19-0 

307 
23-1 

— 

_ 

— 

;B 

Alcohol. 
Water. 

64,091 
65,189 

28-61 
29-10 

9-0639 
0-0567 

o-47 
0-46 

20-4 
18-9 

24-9 
24-4 

— 

— 

— 

-  36 
+  59 

Alcohol  . 
Water. 

64,159 
65.394 

28-64 
29-19 

0-0596 
0-0667 

0-50 
0-54 

7-25 
8-25 

107 
K'S 

7-7981 

7-7456 

0-0525 

+3" 
+  320 

Air. 
Paraffin. 

59,o8i 
66.355 

26-37 
29-62 

0-0624 

0-0715 

0-50 

0'53 

I5-4 

8-75 

19-4 
n-8 

7-7985 
7-7930 

7-7425 
7-7284 

0-0460 
0-0646 

+  60 
+323 

Water. 
Paraffin. 

page  loo 
direct   from  HOgbo,  but  were  purchased  in  Stockholm. 


278 


THE  PRACTICAL  PHYSICS  OF 


TABLE  LI  1 1.  continued. — RESULTS  of  EXPERIMENTS  on  the  TENSILE 

All  the  bars  tested  were  filed  in  the  middle  to  smaller 

Those  bars  preceded  by  a  bracket    j    were 


Sample  Bars. 

Section  of  the  b;ir 
whereitwasnot  filed. 

Mean  area 

of  the 

No.  of 

T*'                i 

section 

experi- 
ment. 

Description  of  Steel  or  Iron. 

Carbon. 

Phos- 
^horus. 

Form. 

or 
side. 

where 

filed. 

I  38 

per  cent. 

percent. 

inches. 

sq.  in. 

English  puddled  iron  from  Low  M  or    

0'2I 

0-068 

Round  . 

0-465 

O-0823 

139 



•' 

0-0807 

(40 

0-I062 

(41 



„ 

',', 

- 

0-0784 

I  42 

from  Middlesbrough-on-Tees  ... 

0-07 

0-25 

„ 

0-581 

0-I909 

143 



» 

" 

" 

0-18I5 

(44 

„ 

it 

H 

OT933 

(45 



',', 

" 

" 

o-i  88  1 

(47 



- 

" 

" 

O'l  8So 
0-1990 

S 



"n 

n 

" 

o-n-)4<> 

49 



» 

n 

- 

0-1913 

(So 

\51 
I52 
1  53 

Puddled  iron  from  Motala  (Sweden) 

0'2 

0'02 

" 

0-465 

o-  1  1  o 
0-1214 
o-  1  off.) 

0  1210 

" 



„ 

„ 

M 

{54 

n 

0-II76 

55 

... 

<t 

OIK/) 

56 

0-1188 

Jr* 

57 

;j 

j] 

"t 

o-  1  207 

58 

o-i  145 

(59 

„            from  Surah  am  mar,  N.P  

O'l  169 

J  60 

0-1031) 



- 

~ 

-, 

„ 

0-1135 

J62 

1  63 

Iron  made  in  the  charcoal  hearth  from  Ayi  d  (Sweden)  j 

0-07    / 

to  o-i  8  ( 

O'26 

Square  . 

" 

o'iSio 
0-1819 

(64 

Us 

166 
(67 

" 

» 

" 

'' 

" 

Q-I373 
0-1373 
0-1341 
0-1326 

/      | 

Iron  made  in  the  Lancashire  hearth  from  Lesjoforss  \ 

0-06 

0'O22 

0-1845 

J  Do  j 

(Sweden)     J 

(69 

„ 

„ 

- 

„ 

0-1800 

(70 

0-07 

0-1633 

!, 

,, 

H 

" 

0-1613 

f  722 

„ 

n 

H 

0-1303 

1732 

" 

" 

,',' 

" 

" 

o'i  199 

1  Compare 
2  Nos.  72  and  73  wrere  taken  from  the  previously  broken  bar,  No.  41  in  Table  IV.,  which 


THE  MODERN  STEAM  BOILER. 


279 


STRENGTH  of  Iron  and  Steel  at  DIFFERENT  TEMPERATURES. 

dimensions  for  a  length  of  from  4  to  6  inches. 
originally  parts  of  the  same  bar. 


Ratio 

Elongation  by 

Specific  gravity  determined 

between 
the  area  of 

rupture. 

after  the  experiment. 

Tempera- 

Hreakini; \\eiglit  per 
s>.|    ir.c  i  of  the 
utigii.al   mean  area 
of  the  filed  part 
oi  the  bar. 

Area  of 

fracture. 

fracture 
and  the 
original 

area  of  the 

hied  part. 

Excluding 
the  inch 
where  the 
fracture 
took  place. 

On  a 

length  of 
^•2  inches, 
the  place 
of  fracture 
included,  i 

Of  the 

part  not 
filed. 

Of  the 

hied  part. 

Difference 
between 
the' 
specific 
gravities. 

ture  of 
the  bar 
uring  the 
experi- 
ments. 

The  bar 
broken  in. 

Ibs. 

tons. 

scj.  in. 

per  cent. 

per  cent. 

Fahr. 

57,366 

25-60 

0-0401 

0-49 

23-5 

23-8 

+   53 

Water. 

65,394 

29-lQ 

0-0425 

0-53 

9'0 

11-8 

7-7833 

77142 

0-0691 

+  275 

Paraffin. 

60,  }  1  6 

26-92 

0-0567 

o'53 

20  -Q 

24-2 

7-7878 

77404 

0-0474 

+  55 

\\  ater. 

67,316 

30-05 

0*0462 

0'59 

11-5 

13-2 

7-7889 

77671 

O'O2l8 

+  280 

Paraffin. 

61483 

27-44 

o'f  177 

0-62 

24-7 

29-2 







-  40 

All  ohol. 

57,846 

25-81 

o'io6o 

0-58 

19-6 

23-9 

— 

— 

— 

+  57 

Water. 

63,885 

28-60 

0-1177 

0-6  1 

23-I 

26-8 







-  27 

Alcohol. 

59,287 

26-46 

0-1257 

0-67 

20-8 

24-5 

— 

— 

— 

+  59 

Water. 

52,S37 

23-58 

0-1341 

0-71 

9-7 

I2'2 

7-6808 

7-6033 

0-0775 

+  60 

Ditto 

55,010 

24-60 

0-1099 

0-55 

20-8 

24-1 

7-6782 

7-4807 

0-1975 

+  62 

Ditto. 

'"',71  7 

3  1  '  1  2 

O'I2l6 

0-62 

14-5 

17-0 

7-6885 

7.5646 

0-1239 

+3'8 

Paiaffin. 

''2,55'' 

27-92 

— 

— 

88 

10-6 

7-6780 

7-5629 

0-1151 

+419 

Ditto. 

54.14" 

24-'7 

0-0513 

0'45 

2i'5 

25-8 







-  16 

Alcohol. 

Jl'121 

22-82 

00626 

16-3 

20-8 



_ 



+  60 

Water. 

63,336 

28-27 

00747 

0-71 

8-1 

— 

— 

— 

— 

+320 

Paraffin. 

68414 

30-54 

0-0762 

0-63 

157 

I7-5 

— 

— 

— 

+  392 

Ditto. 

68482 

3o-=i7 

0-0580 

0-49 

2i'3 

243 

_ 

_ 

_ 

-  27 

Alcohol. 

50,367 

22-48 

00667 

0.56 

iro 

— 

7-7177 

7-6921 

0-0256 

+  53 

Water. 

53,111 

23-71 

0-0609 

0-51 

16-3 

19-1 

77359 

7-7091 

0-0267 

+  60 

Ditto.     - 

''5,394 

29-19 

0-0715 

Q'59 

9-6 

77159 

7-7065 

0-0094 

+347 

Air. 

63,U9 

28-21 

0-0624 

o-55 

8-0 

— 

7-7294 

7-7032 

0-0262 

+374 

Ditto. 

50,710 

22-63 

0-0654 

0-56 

16-8 

18-5 







-  24 

Alcohol. 

46,310 

20-67 

00413 

0-40 

I1'2 

15-2 

7-7918 

7-7105 

0-0813 

+  53 

Water. 

57,160 

25-51 

0-0540 

0-48 

9-7 

13-1 

7-7762 

0-0304 

+338 

Air. 

64,159 

28*64 

0-1257 

0-69 

187 

29-9 

77424 

7-6699 

0-0725 

+  55 

W.uer. 

79*667 

35-56 

0-1257 

ofx; 

157 

- 

77657 

7-7114 

0-0543 

+302 

Paraffin  . 

66,286 

29-59 

0-0914 

0-66 

17-3 

20-4 







-   16 

Alcohol. 

67,59° 

30-17 

0-1099 

0'8o 

20-9 

2i'5 

: 





—   ii 

Ditto. 

63,130 

73.560 

28-18 
32-83 

0-0654 
0-0684 

0-49 
0-52 

16-5 

I9-5 

20'2 

— 

— 

— 

+  55 
+275 

Water. 
Paraffin. 

55.37'' 

2471 

0-0684 

0-37 

22-5 

31-6 

— 

— 

— 

-  27 

Alcohol. 

51,053 

22-79 

0-0624 

0-35 

27-7 

— 

— 

— 

— 

+  60 

Water. 

44,328 
62,169 

19-78 
27-79 

0-0401 

0-0624 

0-25 
0-39 

25-4 

]5'i 

2O'2 

7-838I 

7-8I35 
7-8339 

0-0322 
0-0042 

+  57 
+3H 

Ditto. 
Paraffin. 

56,199 

62,718 

28-00 

0-0527 
0-0596 

0-41 
0-49 

107 
8-0 

I7-2 
11-3 



- 

- 

+  55 
+330 

Water. 
Paralrin. 

page  100. 

accounts  for  th"  breaking-load  being  greater  than  for  the  other  bars  of  the  same  kind  of  iron. 


280  THE  PRACTICAL  PHYSICS  OF 

"  In  this  Table  we  have  given,  as  a  measure  of  extensibility, 
the  percentage  elongation  after  fracture,  calculated  partly 
on  the  measured  and  divided  portion  of  the  bar  at  which 
fracture  did  not  occur,  and  partly  on  the  entire  length  of  the 
divided  portion,  if  the' bar  was  not  ruptured  beyond  the  outer 
divisions.  .  .  . 

"  From  this  Table  it  is  seen  that  among  all  the  bars  broken  at 
very  low  temperatures  only  one,  viz.,  the  cast  steel  bar  No.  18, 
broke  with  a  smaller  load  than  was  necessary  to  fracture  another 
portion  of  the  same  bar  at  the  ordinary  temperature.  In  this 
case,  however,  the  difference  between  the  two  breaking  weights 
is  too  insignificant  to  demand  attention,  and,  moreover,  an  oppo- 
site result  was  obtained  writh  another  bar  of  the  same  make,  No. 
20.  In  general,  the  extensibility  has  not  been  found  less  at  low 
than  at  ordinary  temperatures.  On  the  contrary,  at  higher  tem- 
peratures, between  212°  and  392°  F.,  the  absolute  strength  of 
iron  is  considerably  greater  than  at  ordinary  temperatures,  as 
Dr.  Fairbairn  also  found  in  his  experiments  ;  but,  on  the  other 
hand,  the  extensibility  appears  to  be  somewhat  diminished.  In 
steel,  however,  there  does  not  seem  to  be  any  essential  difference, 
either  in  absolute  strength  or  in  extensibility  within  the  range  of 
temperature  mentioned. 

"  The  greatest  increase  of  strength  by  elevation  of  temperature 
was  found  in  those  kinds  of  iron  which  contained  but  little 
carbon  ;  and  in  order  to  ascertain  that  this  result  was  not  acci- 
dentally occasioned  by  the  filed  portions  of  the  bars  having 
been  harder  than  the  rest,  \ve  determined  the  amount  of  carbon 
at  the  place  of  fracture  in  the  bar  numbered  71  in  Table  LI  1 1., 
this  bar  having  been  ruptured  in  a  paraffin  bath.  The  pro- 
portion of  carbon  in  that  part  wTas  found  to  be  0^07  per  cent., 
and  therefore  was  not  greater  than  in  other  bars  of  the 
same  kind  of  iron.  From  this  experiment,  as  well  as  from 
those  performed  in  hot  air  with  the  cast  iron  apparatus,  it  is 
manifest  that  the  increased  strength  exhibited  by  iron  at  high 
temperatures  cannot  be  referable  to  any  chemical  influence  or 
carbonisation  exerted  by  the  paraffin  on  the  iron  during  the 
experiment. 

Effect  on  Specific  Gravity. — 4<  As  it  is  well  known  that  the  specific 
gravity  of  iron  is  diminished  by  stretching  at  ordinary  tempera- 
tures, we  considered  it  would  be  of  interest  to  determine  whether 


THE  MODERN  STEAM  BOILER.  281 

the  same  effect  is  produced,  and,  if  so,  in  what  manner,  when 
the  traction  is  performed  at  other  temperatures.  For  this 
purpose  we  have  taken  the  specific  gravities  of  some  of  the  bars 
mentioned  in  Table  LI  1 1.,  after  fracture,  examining  both  the  filed 
portion  and  the  original  unfiled  part,  which  in  general  has  not 
suffered  any  perceptible  alteration  by  stretching.  It  was  be- 
lieved that  from  these  determinations  some  explanation  might 
possibly  be  found  of  the  very  remarkable  quality  which  iron 
possesses  of  becoming  stronger  at  certain  degrees  of  heat  than 
at  ordinary  temperatures.  As  seen,  however,  from  Table  LIII., 
there  is  generally  no  great  difference  between  the  diminutions 
of  specific  gravity  when  the  fracture  by  extension  was  performed 
at  different  degrees  of  temperature." 

Effect  on  Modulus  of  Elasticity, — Tables  LIV.  and  LV.,  which 
follow,  show  the  results  of  experiments  made  to  determine  "  in 
what  manner  the  position  of  the  limit  of  elasticity,  and  the  value 
of  the  modulus  of  elasticity  in  iron  and  steel,  are  dependent  on 
the  temperature  at  which  tension  is  performed." 

The  apparatus  used,  and  the  precautions  to  ensure  accuracy 
which  were  adopted,  are,  as  in  all  cases,  fully  described  by 
Professor  Knut  Styffe,  but  to  follow  these  his  book  must  be 
referred  to. 

The  following  are  some  extracts  of  general  importance  : — 

"The  position  of  the  limit  of  elasticity  in  iron  and  steel  is  in 
a  great  measure  dependent  on  the  mechanical  treatment  to  which 
the  material  has  been  subjected  and  on  the  temperature  to  which 
it  has  been  subsequently  exposed.  This  limit  can  never,  there- 
fore, be  known  \vith  accuracy  without  a  special  determination, 
and  by  such  a  determination  the  limit  itself  is  raised.  It  has 
been  found  that  with  a  bar  which  has  been  extended  beyond  its 
limit  of  elasticity  the  position  of  the  new  limit  might,  under 
ordinary  conditions,  be  easily  determined  by  representing  the 
permanent  elongations  graphically  ;  for  the  upper  parts  of  the 
curves  for  a  new  series  of  experiments  at  the  same  temperature 
will  lie  in  the  continuation  of  the  preceding  curves.  It  was 
therefore  supposed,  at  the  commencement  of  these  experiments, 
that  by  taking  advantage  of  this  circumstance  it  would  be 
possible  to  determine  with  sufficient  accuracy  the  dependence  of 
the  limit  of  elasticity  on  the  temperature  at  which  the  extension 
was  performed.  For  such  a  purpose,  therefore,  the  limit  of 


282 


THE  PRACTICAL  PHYSICS  OF 


TABLE  LIV.— RESUITS  OK  EXPERIMENTS  to  ascertain  in  what 

affected  by  the  TEMPERATURE  at 

The  bars  tested  were  each  about  six  feet  long,  and  filed  in  the 


Amount  of  carbon. 

No.  of 
bar 

Description  of  steel  or  iron. 

Treatment  of  the  bars  immediately  before  they 
were  tested. 

In  the  bar 

In  bars  of 
the  same- 

tested. 

kind. 

per  cent. 

per  cent. 

Hammered     Bessemer     steel     from 

I 

Hogbo,  marked  1-2  :— 
ist  experiment    ... 

j  Heated  to  slight  redness  and  slowly  \ 
1      cooled                          .         ...         ...  j 



I'35 

Same  bar      ...     2nd            „ 

Heated  ^hour  in  paraffin  at  266°  Fahr 

_ 

,, 

...     3rd            

Do.                do.                do. 

— 

„ 

M 

...     4th 

... 

— 

,, 

" 

...     5th 

... 

-  — 

...     6th 

Do.                do.                284°  F. 

— 

,, 

7th 

J  Heated  for  2  hours  in  paraffin  at  \ 

" 

...     8th 

\      275°  Fahr                                       .    j 

M 

...     Qth            

Heated  and  slowly  cooled     



" 

H 

...    loth            

... 

—  . 

,, 

„ 

...    iith 

— 

Hammered  Bessemer  steel  from  Hogbo, 

marked  with  the  old  No.  3-5  :  — 

2l 

ist  experiment     ... 

1-26 

— 

" 

Same  bar      ...     2nd        •   „ 

... 

H 

— 

...     3rd 

M 

•  — 

...     4th            

... 

— 

H 

...     5th 

(  Heated  to  slight  redness  and  slowly  ) 
t      cooled  j 

„ 

— 

p 

...     6th 

Cooled  for  £  hour  at                9°  Fahr. 

M 

— 

...     7th 

n 

— 

„ 

...     8th 

... 

„ 

— 

Hammered  Bessemer  steel  from  Hogbo, 

marked  09:  — 

3 

ist  experiment     ... 

... 

— 

I  '05 

Same  bar      ...     2nd            ,, 

— 

...     3rd 



"; 

...     4th 

Slightly  heated  and  slowly  cooled  ... 

— 

,, 

,, 

...      5th 

— 

Rolled  puddled  steel  from  Surahammar, 

marked  B  i  :— 

4 

ist  experiment     ... 

... 

066 

— 

" 

Same  bar      ...     2nd            „ 

M 

— 

-.     3rd            

... 

n 

— 

...     4th 

• 

— 

'n 

5th 

... 

H 

— 

„ 

...     6th 

... 

„ 

— 

Rolled  puddled  steel  from  Suraljammar, 

marked  N  i  :  — 

5 

ist  experiment     ... 

... 

0-56 

— 

Same  bar      ...     2nd 

... 



...      3rd 

... 

"n 



" 

...      4th 

... 

1  — 

1  The  bar  No.  2  was  not  filed  in  the  middle,  but 
This  bar  had  been  previously  used  for  other  experiments,  and 


THE  MODERN  STEAM  BOILER. 


283 


degree  the  LIMIT  of  ELASTICITY  on  Stretching  Iron  or  Steel  is 

which  the  Extension  is  performed. 

middle  for  a  length  of  about  four  and  a  half  feet.     (See  p.  106). 


Difference 

The  original  section 

as  to 

The  filed  nidclle 
part  as  to 

Average 

between  the 
average 

Limits  of  elasticity. 

Elongation 
of  the  middle 

emperature 
during  the 
experiment. 

temperature 
during  the 
experiment 
and  the 

filed  part  of 
the  bar 
during  each 
experiment. 

Form. 

Diameter 

Length. 

Sectional 
area. 

Calculated 
according 
to  the 

Found 
to  be. 

Consequently. 

temperature. 

x  peri  men  ts. 

Higher. 

Lower. 

inch. 

feet. 

sq.  inch. 

Fahr. 

Fahr. 

bs.  persq.  in. 

Ibs.  per 
sq.  in. 

Ibs.  per 
sq.  in. 

Ibs.  per 
sq.  in. 

per  cent. 

Round. 

0-488 

0-1679 

+    62 

61,414 

0-367 

,, 

+   68 

+      6 

74,109 

81,657 

7,548 

— 

0-060 

M 

,, 

+    55 

—     3 

82,481 

82,481 

0 

0 

0081 

" 

" 

" 

" 

+  264 
+   62 

+  109 

—  102 

83,510 
79,873 

79,256 
78,226 

z 

4,254 
1,647 

0-027 
0-521 

„ 

„ 

„ 

,, 

+    62 

0 

78,913 

76,991 

— 

1,992 

0065 

„ 

„ 

„ 

» 

+  266 

+  204 

78,569 

91,607 

13,038 

— 

0-030 

,, 

M 

„ 

+  57 

-209 

92,842 

96,960 

4,118 

— 

0-047 

?, 

,, 

+  64 

61,758 

. 

— 

0-104 

n 

,, 

,, 

,, 

—       2 

-  66 

72,188 

79,736 

7,548 



0-092 

" 

" 

" 

» 

+  55  . 

+  57 

82,344 

69,992 

12,352 

0105 

Square. 

0-372 

5l 

+  64 

67.833 

o  150 

,, 

,, 

„ 

+  249 

+  185 

71,158 

68,414 

— 

2,744 

0367 

,, 

,, 

,, 

,, 

+  278 

-194 

+  223 

70,404 
77,540 

76,579 
73,766 

6,175 

3,774 

0-099 

O'2OI 

,, 

„ 

+  59 

- 

— 

65.189 

— 

— 

0-143 

„ 

,, 

+  46 

-   13 

66,561 

66,56i 

0 

0 

0-II3 

,, 

H 

—   ii 

-  57 

67,933 

70,678 

2,745 

— 

0-085 

" 

" 

•i 

" 

+  50 

+  39 

71,364 

67,590 

— 

3,774 

0-17I 

Round. 

0-465 

4-62 

O-II56 

4-  57 

64,502 

O.I30 

,, 

„ 

—    22 

-   79 

69,306 

72,737 

3.43' 

— 

O-126 

,, 

,, 

+    59 

+  81 

69,649 

— 

— 

0-204 

,, 

H 

n 

„ 

+  269 

+  210 

75,825 

85,431 

9,006 

— 

O-I7I 

>, 

„ 

-, 

+  60 

-209 

88,176 

90,921 

2,745 

— 

0.762 

Round. 

0'5 

4'37 

0-I2I4 

+  57 

46,318 

O'HO 

,, 

,, 

—    22 

-  79 

50,435 

53,i8o 

2,745 

— 

o  187 

,, 

N 

+     51 

+  73 

57,983 

55,239 

— 

2,744 

0-289 

,, 

„ 

+  266 

+  215 

62,444 

62,444 

o 

0 

0-320 

,, 

,, 

+  53 

-213 

68,620 

70,335 

1,715 

— 

0-241 

» 

» 

- 

» 

+264 

+  211 

72,737 

71,364 

— 

1,363 

0-307 

Square. 

0-4/6 

4'49 

0-1561 

+  59 

0-303 

,, 

,, 

+  275 

+  216 

43,573 

46,318 

2,745 

— 

0-324 

,, 

+  53 

—  222 

53,043 

55,444 

2,401 

•  — 

0-318 

" 

» 

-  27 

-    80 

56,61  1 

59,oi3 

2,402 

0-396 

was  of  the  same  thickness  throughout  the  five  feet. 

thereby  elongated,  which  accounts  for  the  high  limit  of  elasticity. 


284 


THE  PRACTICAL  PHYSICS  OF 


TABLE  LIV.  continued. — RESULTS  of  EXPERIMENTS  to  ascertain  in 

affected  by  the  TEMPERATURE  at 

The  bars  tested  were  each  about  six  feet  long,  and  filed  in 


Amount  of  carbon. 

No  of 
bar. 

Description  of  Steel  or  Iron. 

Treatment  of  the  bars  immediately  before  they 
\vere  tested. 

In  the  bar 

In  bars  of 
the  same 

tested. 

kind. 

per  cer.t. 

per  cent. 

Rolled  puddled  steel  from  Surahammar, 

marked  N  P  2  :— 

6* 

ist  experiment     ... 

... 



07        • 

n 

Same  bar      ...     2nd            „ 

f  Heated  for   A  hour  in   paraffin   at  ) 
1         284°Fahr    f 

_ 

...     srd 

Do,        do.        at302°Fahr.... 



„ 

-     4th            

f  Heated  for  25  minutes  in  paraffin  ) 
t         at  266°Fahr  j 

— 

„ 

a 

5th 

... 



H 

,, 

...     6th 

— 

„ 

Rolled  puddled  iron  from  Low  Moor  :  — 

T 

ist  experiment    ... 

... 

— 

0'2 

Same  bar      ...    and 



„ 

...     3rd 

.      ... 

— 

„ 

Rolled  puddled  iron  from  Motala 

(Sweden)  :— 

8 

ist  experiment     ... 
Same  bar      ...     2nd            „ 

... 

— 

02 

...     3rd            

•    ... 



|| 

" 

, 

...     4th           

... 

— 

Rolled  puddled  iron  from  Motala 

(Sweden)  :— 

9a 

ist  experiment     ... 

... 



0'2 

Same  bar      ...     2nd 



" 

...     3rd 

'*'                  \"                 '" 

.  

H 

-     4th            

... 

_ 

" 

5th            



u 

...     6th 

Heated  to  redness  and  slowly  cooled 



„ 

...     7th            

f  Heated   for    A  hour  in  paraffin  at  \ 
\     284°  Fahr  f 

— 

„ 

.     8th 

>B 



Jl 

" 

9th 



" 

...   loth 

(  Heated   for   A   hour  in  paraffin   at  } 
t      284°  Fahr                                            j 



...    nth 

,  

„ 

...    I2th 

... 

— 

„ 

Rolled  puddled  iron  from  Surahammar, 

marked  N  H  :— 

10 

ist  experiment     ... 



02 

Same  bar      ...     2nd            „ 

.".                  ... 



,',' 

...     3rd 

... 

— 

H 

Rolled  iron  made  in  charcoal-hearth  at 

Ayrd  (Sweden)  :— 

ii 

ist  experiment     ... 

... 



O'l 

Same  bar      ...     2nd            ,, 



" 

-     3rd 

... 

" 

" 

This  bar  had  been  previously  used  for  other  experiments 


THE  MODERN  STEAM  BOILEK. 


285 


what  degree  the  LIMIT  of  ELASTICITY  on  Stretching  Iron  or  Steel  is 

which  the  Extension  is  performed. 

the  middle  for  a  length  of  about  four  and  a  half  feet. 


The  original  section 
as  to 

The  filed  middle 
part  as  to 

Average 

Difference 
between  the 
average 

Limit  of  elasticity. 

Elongation 
of  the  middle 

temperaturt 
during  the 

temperature 
during  the 

filed  part  of 
the  bar 

Calculated 

Form. 

or  side. 

Length. 

Sectional 
area. 

experiment. 

experiment 
and  the 
previous 
temperature. 

according 
to  the 
previous 
experiments 

Found 
to  be. 

Consequently. 

during  each 
experiment. 

Higher. 

Lower. 

inch. 

feet. 

sq.  inch. 

Fahr. 

Fahr. 

Ibs.  per  sq.  ii 

Ibs.  per 
sq.  in. 

Ibs.  per 
sq.  in. 

Ibs.  per 
sq.  in. 

per  cent. 

Square. 

0-488 

4'50 

0-2163 

4-   62 

0-106 

„ 

,, 

„ 

„ 

+    62 

o 

62,444 

68,276 

5,832 

— 

0-044 

„ 

„ 

„ 

„ 

+•  57 

-     5 

71,776 

71,776 

0 

0 

0-048 

n 

H 

H 

4-  68 

4-   ii 

72,599 

72,051 

— 

548 

0-066 

4-237 

4-169. 

74,795 

68,620 



6,175 

0-079 

» 

» 

n 

+  64 

-173 

69,992 

71,707 

1,715 

0-082 

Round. 

o-5 

4-72 

0-1256 

4-298 

4I5I52 

0-476 

M 

n 

4-  5i 

-247 

42,201 

46,318 

4-H7 

— 

0-986 

.' 

-   16 

-  67 

48,377 

50,435 

2,058 

— 

0-179 

Round. 

0-476 

4-65 

O-I229 

+  57 

34-172 

0-256 

n 

n 

B 

|( 

4-267 

+  2IO 

36,368 

34-035 

— 

2,333 

0-57I 

,, 

,, 

+  57 

—  210 

35,339 

39,662 

4,323 

0-I5I 

" 

" 

" 

" 

+  278 

4-221 

40,142 

35,339 

4,803 

0705 

Round. 

0-476 

4  '49 

0-III2 

4-284 

34,4472 

0-276 

„ 

„ 

4-  57 

—  227 

35,8i9 

39,250 

3,43i 

— 

0-374 

n 

,, 

- 

,, 

+  275 

4-218 

39,799 

35,270 

— 

4,529 

0-379 

+  64 

—  211 

37,260 

42,132 

4-972 

0-978 

„ 

„ 

,, 

-     5 

-    69 

42,544 

45,289 

2,745 

— 

0-230 

„ 

„ 

,, 

4-  60 



— 

27,448 

— 

— 

0-294 

„ 

,, 

„ 

+  64 

+     4 

28,134 

31,565 

3,431 

— 

0-484 

n 

H 

n 

(| 

4-264 

4-  200 

33,344 

29,369 



3,975 

0-276 

„ 

„ 

4-  60 

-204 

29,918 

33,898 

3,98o 

O'i6i 

„ 

„ 

„ 

„ 

4-  64 

+     4 

34.653 

33,966 

— 

687 

0-093 

n 

„ 

n 

u 

4-271 

4-207 

34-653 

29,849 



4,804 

0-390 

" 

" 

» 

» 

4-  66 

-195 

30,535 

34-653 

4-n8 

— 

0-935 

Round. 

0-476 

0-I269 

+  57 

28,134 

0-103 

,, 

,, 

H 

i( 

-   18 

-  75 

29,506 

32,594 

3,088 

— 

O'2=j6 

" 

M 

» 

4-300 

4-318 

35,956 

28,820 

— 

7,136 

0-138 

1  Square. 

0-5II 

4'49 

0-2087 

4-  53 

_ 

_ 

45,426 

_ 

_ 

0-358 

„ 

,, 

„ 

—    22 

-  75 

46,455 

49,886 

3.431 

— 

0-630 

" 

" 

" 

" 

4-  50 

4-  72 

50,092 

47,347 

2,745 

0-328 

thereby  elongated,  which  accounts  for  the  high  limit  of  elasticity. 


286 


THE  PRACTICAL  PHYSICS  OF 

TABLE  LV.— RESULTS  of  EXPERIMENTS  for  DETERMINING  the  MODULUS 


Amount  of  carbon. 

Section  as  to  i 

The  bar 

Specific 

had  just 

No. 
of 
the 

Description  of  Iron  or  Steel. 

gravity 
of  the 
bar. 

In  the 

bar  tested. 

In  bars  of 
the  same 
kind. 

Form. 

Mean  area 
before  the 
experi- 
ment. 

When  the  bar 
has  not  been 
heated. 

before  th 
modulus 
was  takei 

obtained  : 

lar. 

perman- 

ent elong 

ation  of 

per  cent. 

percent. 

square 
inch. 

Ibs.  per 
square  inch. 

per  cent. 

Hammered  Bessemer  steel  from  Hogbo  — 

I 

Marked  1*2                                 •••        ••• 

7-832 

— 

1  "35 

Round. 

0-1823 



2-" 

f           „        with  the  old  number  of  hard-  ) 
\     ness  3-5.    The  bar  No.  2  Table  LIV.     j 

7-850 

1-26 

Square. 

0-IOI5 

30,124,180 

0-004 

3 

(                    0-9.    The  bar  No.  3  in  Table  ) 
1      LIV  j 

7-849 

- 

1-05 

Do. 

0-II56 

30,604,520 

0-014 

Hammered  Bessemer  iron  from  Hogbo  — 

4" 

/      Marked  with  the  old  number  of  hard-  \ 

7-878 

O'l 

— 

Do. 

0-1003 

32,320,020 

0'O02 

ei 

\         ness  5     j 

7-879 

0-15 



Do. 

O-I1O7 

34,241,380 

O'OOI 

9* 

Rolled  cast-steel  from  Wikmanshyttam  — 

6 

Degree  of  hardness  No.  i        

7-832 

I'22 

— 

Round. 

0-1691 

31,222,100 

0'021 

Hammered  cast-  steel  from  F.  Krupp  — 

7 

Marked  with  two  crowns        

7^43 

— 

o-6i 

Do 

0-2065 

31-359,34° 

0-0008 

8 

Rolled  puddled  steel  from  Surahammar— 
(Marked    B    i.         The    bar    No.    4    in  1 
|      Table  LIV             .          j 

7781 

0-66 

Square. 

0-1214 

9 

f  Marked    N    i.         The    bar    No.    5    in  \ 
\     Table  LIV                                                  J 

7-828 

0-56 

Do. 

0-1561 

29,918,320 

0027 

10 

Rolled  puddled  iron  — 
From  Low  Moor            

7-780 

_ 

O'20 

Round. 

0-1961 

31,976,920 

0-006 

j  i 

Dudley                              .  . 

7-463 



o'og 

Do. 

0*1844 

28,408,680 

o'ooS 

12 

7'444 

O'OO 

Do. 

O"2OO6 

•77    i  i  fi  OOO 

o'o77 

13 

„     Motala  (Sweden)  

/   ^TT"H 

7734 

0-05 

Do. 

0-1942 

^/j44°'uuu 
30,261,420 

0008  ' 

14 

f                                           The  bar  No.  8  in  ) 
|             Table  LIV    J 

7734 

_ 

0'2 

Square. 

0-1229 

29,575,220 

_ 

15 

From  Surahammar,  marked  N 

7789 

0-14 

- 

Do. 

0-2176 

31,084,860 

0-018 

16 

f         „                                      „        N  H.         \ 
\         The  bar  No.  10  in  Table  LIV.        ...  j 

7-807 

- 

0'2 

Do. 

0-1269 

30,467,280 

0-002 

Rolled  iron  made  in  charcoal-hearth  — 

17 

j      From  Arvd  (Sweden).    The  bar  No.  1  1  ) 
t         in  Table  LIV  j 

7-780 

— 

0-07  to 
0-18 

Do. 

0-2087 

26,761,800 

0-037 

18 

„ 

7-761 

- 

Do. 

Do. 

0-2279 

27,791,000 

0-003 

Rolled  iron  made  in  charcoal-hearth  — 

19 

From  Hallstahammar  (Sweden) 

7-829 

— 

0-07 

Do. 

0-1891  . 

28,957,640 

0-0  1  '; 

20 

7-854 

— 

0-07 

Do. 

0-1965 

30,810,380 

O'OOi 

For  the  bars  in  Table  LIV.,  which  were  filed  to  smaller  dimensions  in  the  middle,  this  table  shows 
The  influence  of  the  permanent  elongation  on  the  modulus  of  elasticity  was  first  examined  after  the 

be  referred  to  the  value  obtained  af'er  heating. 
The  bars  Nos,  2,  4,  and  5,  were  not  ordered  at  Hogbo,  but  we.re  purchased  i,n  Stockholm, 


THE  MODERN  STEAM  BOILER. 

of  ELASTICITY  in  Iron  and  Steel  by  TRACTION. 


287 


The  Modulus  of  Elasti< 


When  the  bar 
1      had  been 
leated  to  slight 
redness. 

The  bar 

had  just 
before  the 
modulus 
vas  taken 
blamed  a 
perman- 
nt   elong- 
ation of 

Dimin- 
ished by 
the  bar 
having 

under- 
gone per- 
manent 
longation 

The  per- 
manent 
longation 
vhich  the 
bar  had 
obtained 
shortly 
before. 

Diminu- 
tion. 

By  an  increase  of 
temperature. 

Dimin- 
ished on 
an  aver- 
age for  an 
ncrease  of 
tempera- 
ture of 
•8°F.^B. 

Increase. 

By  reduction  of  the 
temperature. 

Increase 
on  an 
average 
fora 
decrease 
of  tem- 
perature 
of  i  8° 
F.  —  B. 

From 

To 

From 

To 

Ibs.  per 
square  inch. 

per  cent. 

0-003 

per  cent. 

per  cent. 

per  cent. 

Fahr. 

Fahr. 

per  cent. 

per  cent. 

Fahr. 

Fahr. 
-  9 

per  cent. 
0-015 

31,839,680 

6-4* 

0-58 

_ 



_ 

— 

0'5 

+  5° 

30,535-900 

0-006 

4'92 

0-66 

3-8 

+  55 

+  271 

0-031 

re 

+  48 

-22 

0-025 

31,496,580 

oooo 

9-24= 

0-72 

- 

- 

- 

- 

- 

- 

- 

- 

34,584,480 

O'oi7 

6'5 

o'6i 

— 



- 



— 



- 

- 

- 

- 

8-6 

0-7 

4-2 

+60 

+  275 

0-035 

- 

- 

- 

- 

32,114,160 

0-004 

6-2 

0-78 

3-8 

+  59 

+  264 

0-033 

I'2 

+  50 

-II 

0-035 

30,330,040 

O'OIS 

- 

- 

- 

- 

- 

- 

2'I 

+  51 

-27 

0-047 

— 

— 

57 

O'i6 

— 

— 

— 

— 

— 

— 

— 

— 

- 

- 

6-6 

177 

- 

- 

- 

- 

- 

- 

- 

- 

30,77^,000 

0001 

776 

0-72 

— 

- 

— 

— 

— 

- 

— 

- 

- 

- 

- 

5-o 

+  59 

+  284 

0-040 

I'9 

+  48 

-25 

0*046 

:;   - 

30,741,760 

0-003 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

i 

— 

4'3 

o'54 

— 

— 

— 

— 

2'O 

+  55 

+  25 

0-044 

29,232,120 

0003 

0-78 

0-32 

- 

- 

- 

- 

- 

- 

- 

- 

- 

— 

— 

— 

37 

+  59 

+  262 

0'033 

— 

— 

— 

— 

30,810,380 

0000 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

'only  the  form  and  the  mean  area. 

had  been  heated,  and  hence  the  percentage  diminution  of  the  modulus  which  is  here  given  should 


288  THE  PRACTICAL  PHYSICS  OF 

\ 

elasticity  should  be  determined  for  each  bar,  first  at  the  ordinary 
temperature  and  then  at  a  very  low  or  high  temperature  ;  the 
curves  of  elongation  for  both  series  should  afterwards  be  traced, 
and  finally  that  point  determined  at  which  the  tangent  to  the 
upper  part  of  the  curve  of  the  latter  series  cuts  the  ordinate  of 
the  terminal  point  of  the  former.  The  length  of  that  portion  of 
the  ordinate  lying  between  the  tangent  referred  to  and  the  end 
of  the  preceding  curve  would  thus  measure  the  temporary 
elevation  or  depression  of  the  limit  of  elasticity  consequent  upon 
the  difference  of  temperature  at  the  two  experiments.  In  this 
manner  we  have  found  that  the  limit  of  elasticity  in  both  steel 
and  iron  is  always  higher  at  low  temperatures,  and  in  iron  is 
lower  at  high  temperatures,  than  when  the  extension  is  per- 
formed at  the  ordinary  temperature  ;  but  that,  on  the  contrary, 
in  hard  steel  at  a  heat  of  266°  to  302°  F.,  it  is  sometimes  higher 
and  sometimes  lower.  When  the  limit  of  elasticity  in  such  steel 
has  been  found  higher  at  about  284°  than  at  about  59°  F.,  and 
has  been  again  examined  at  the  latter  temperature,  the  result 
has  often  been  somewhat  higher  than  might  have  been  antici- 
pated from  the  experiments  at  high  temperatures.  (Compare 
Table  LIV.,  bar  No.  i,  series  7  and  8,  with  No.  3,  series  4  and  5.) 
This  arose  from  the  fact,  afterwards  observed,  that  when  a 
stretched  bar  is  heated,  even  to  so  moderate  a  temperature  as 
266°  or  302°  F.,  a  change  is  effected  in  the  molecular  condition 
of  the  metal,  which  is  retained  after  the  heat  has  been  removed  ; 
and  therefore  the  limit  of  elasticity  is  often  permanently  altered. 
Since  we  know  that  the  limit  of  elasticity  is  lowered  in  iron  and 
steel  by  annealing,  after  having  been  previously  raised  by 
tension  or  other  mechanical  treatment,  it  was  not  expected  that 
a  moderate  heating  could  raise  the  limit  any  further.  (Compare 
Table  LIV.,  bar  No.  i,  series  2  with  No.  6,  series  2  and  No.  9, 
series  7.)  Sometimes  we  have  even  found  that  the  limit  of 
elasticity  in  stretched  bars  has  been  perceptibly  raised  by 
merely  allowing  the  bar  to  remain  at  rest  for  several  days 
after  stretching.  .  .  .  The  metal  appears  to  acquire  by  this 
means  new  strength  after  having  suffered  from  overstraining. 
On  the  other  hand,  it  has  not  been  found  that  by  cooling  to  a 
very  low  temperature  any  perceptible  permanent  influence  has 
been  exerted  on  the  position  of  the  limit  of  elasticity  in  iron 
and  steel/' 


THE   MODERN  STEAM  BOILER.  289 

11  By  determining  in  this  manner  the  limit  of  elasticity  at  high 
temperatures,  the  temporary  influence  of  the  heat  has  not  been 
ascertained  distinct  from  its  permanent  influence  ;  and  therefore 
the  results  attained  by  the  method  described  above  do  not — at 
least  for  iron — give  any  trustworthy  measure  of  the  temporary 
change  in  the  limit  of  elasticity  by  heating.  As,  however,  the 
subject  has  been  but  very  little  investigated,  we  have  considered 
that  the  results  are  of  sufficient  importance  to  merit  publication. 
In  Table  LIV.  we  have  therefore  given  the  results  of  the 
experiments  with  reference  to  the  position  of  the  limit  of 
elasticity  at  very  low  temperatures,  as  well  as  those  undertaken 
to  determine  the  permanent  influence  of  heating  and  cooling, 
Experiments  on  the  limit  of  elasticity  at  different  temperatures 
should,  however,  show,  with  at  least  sufficient  accuracy  for 
practical  purposes,  by  how  much  the  limit  is  raised  in  iron  and 
steel  when  stretched  at  low  temperatures,  and  within  what  limits  it 
may  vary  when  stretched  at  higher  temperatures  not  exceeding 
302°  F." 

In  experiments  on  the  variation  of  the  modulus  of  elasticity  at 
different  temperatures,  Professor  Knut  Styffe's  method  was  first 
to  determine,  by  several  experiments  at  ordinary  temperatures,  the 
differences  between  the  elastic  elongations  when  the  bar  wa's 
subjected  to  successive  loads,  these  differences  being  reduced 
to  an  average  corrected  by  a  formula  given  by  him.  Then 
similar  determinations  were  made  at  high  or  low  temperatures 
and  were  finally  repeated  at  ordinary  temperature. 

"  If  the  bar  has  not  been  overstretched,  either  previously  or 
during  the  experiment,  the  results  of  the  tension  at  ordinary 
temperatures,  as  performed  before  and  after  heating  or  cooling, 
have  nearly  always  shown  the  closest  agreement  ;  and  we  have 
then  taken  the  average  of  all  these  and  compared  it  with  the 
mean  result  of  the  experiments  at  high  or  low  temperature.  If 
Ej  denote  the  modulus  of  elasticity  at  a  low  or  high  temperature, 
and  Lj  — L0  the  mean  value  of  the  corrected  difference  between 
the  elastic  elongations  obtained  with  loads  Px  and  P0 ;  and  if 
E,  L1  — L,  P1  and  P  represent  corresponding  values  by  tension  at 
the  ordinary  temperatures,  then  wre  obtain — 


29o  THE  PRACTICAL  PHYSICS  OF 

or  if,  as  usually  happened, 


• 

then 


E        L'-L 


The    ratio   ^  is  thus  always  independent  of  the  section  of  the 

bar  ;  and  the  accuracy  with  which  it  may  be  determined 
depends,  when  the  extending  force  is  alike  in  all  the  experiments, 
only  on  the  accuracy  with  which  the  differences  between  the 
elastic  elongations  may  be  measured. 

If  the  bar  has  been  overstretched,  either  before  or  during  the 
experiment,  or  if  it  has  originally  been  much  bent  and  then 
straightened  when  cold,  the  experiments  conducted  at  ordinary 
temperatures  with  the  same  load,  after  a  series  of  experiments 
at  a  higher  (and  sometimes  also  after  those  at  a  lower) 
temperature,  present  less  differences  between  the  elastic  elonga- 
tions than  are  obtained  from  those  which  precede  such  a  series  of 
experiments.  This  results  from  the  influence,  already  alluded 
to,  which  any  great  change  of  temperature  exerts  on  overstretched 
bars,  an  influence  \vhich  partially  restores  the  elastic  force  which 
is  lost  by  overstretching." 

Table  LV.  shows  the  results  of  these  experiments  in  a  collected 
form. 

Influence  on  Flexion.  —  Professor  Styffe  concluded  his  investiga- 
tions by  experiments  testing  the  influence  of  different  tempera- 
tures on  flexion. 

"As  it  was  found,  from  previous  experiments,  that  the 
modulus  of  elasticity  on  tension  is  nearly  alike  in  steel  and  iron 
of  the  same  specific  gravity,  but  that  it  increases  as  the  tempera- 
ture falls  and  diminishes  as  the  temperature  rises,  it  was 
considered  interesting  to  examine  the  influence  which  these 
conditions  would  exert  on  flexion,  because  the  elastic  deflections 
may  be  much  greater  than  the  elastic  elongations  at  tension, 
and  therefore  the  former  admit  of  measurement  with  greater 
accuracy." 

"  In  all  experiments  referring  to  the  influence  of  temperature 
on  the  modulus  of  elasticity,  the  bars  were  tested  first  at  the 
ordinary  temperature,  then  at  the  higher  or  lower  temperature, 
and  finally  again  under  ordinary  conditions.  If  both  series  of 


THE   MODERN  STEAM  BOILER.  291 

experiments  at  the  ordinary  temperature  agree  in  their  results, 
it  is  evident  that  the  change  of  temperature  has  not  permanently 
altered  the  elastic  force  of  the  bar,  but  that  the  differences 
observed  between  the  deflections  at  a  high  or  a  low  temperature, 
and  at  the  ordinary  temperature  have,  therefore,  arisen  only 
from  the  differences  in  the  thermometric  conditions  during 
the  experiment. 

"  If  Ej  and  E0  denote  the  values  of  the  modulus  of  elasticity 
at  two  different  temperatures  /t  and  /0,  and  if  dl  and  d0  denote 
the  measured  differences  of  deflection  with  the  same  load,  and 
a  the  linear  coefficient  of  expansion  of  the  material,  then  we 

Tf 

obtain  with  sufficient  accuracy  the  value  of  the  ratio  ^ 
thus  :—  ^o 


On  the  cooling  of  our  apparatus  from  59°  F.  to—  4°  F.,  we  have 
found  the  mean  value  of  a  =  o-ooooi3,  and  on  heating  from 
59°  F.  to  266°  F.,  a  =  0*00002. 

"The  results  obtained  are  given  in  Table  LVI. 

"In  these  calculations  no  correction  has  been  made  for  change 
of  dimensions  consequent  upon  change  of  temperature  ;  for  the 
measurement  of  the  dimensions  is  generally  taken  at  tempera- 
tures between  32°  and  68°  F.,  and  the  application  of  the  results 
to  particular  cases  would  therefore  have  been  more  difficult  with 
this  correction.  If  a  comparison  be  instituted  between  the  in- 
Huence  of  temperature  on  the  elastic  force  at  flexion  and  at  trac- 
tion, or,  in  other  words,  between  the  values  of  the  coefficients 
/?  and  /3,  given  in  Tables  LV.  and  LVI.,  the  correction  referred  to 
should  in  strictness  be  made  in  both  cases,  although  ft  is  only 
increased  thereby  about  O'ooi  and  /3,  0-004." 


292 


THE  PRACTICAL  PHYSICS  OF 


TABLE  LVI.— RESULTS  of  EXPERIMENTS  to  determine  the 
N.B.— All  the  bars  tested  had  a  length  of  4-3  feet 


Sectiona   area  of 

Sectional  area  of 

Amount  of  carbon. 

bars  not  filed. 

bars  filed. 

pecific 

Rectangular  section. 

ravitv 

+} 

of  the" 

1 

Description  of  Iron  or  Steel. 

bar.  i 

In  the 

n  bars  of 

Diameter 

\verage 

Average 

1 

ar  tested. 

he  same 
kind. 

or  side. 

width. 

height. 

"o 
<5 

per  cent. 

per  cent. 

in. 

in. 

in. 

Hammered  Bessemer  steel  from  Hogbo  — 

j 

7-868 







. 

•'  0-48 

O'  1800 

r 

f      Marked  with  the  old  No.  of  hardness  ) 
t         3-5,  the  bar  No.  2  in  Table  LV.       ...  J 

7-850 

1-26 

- 

- 

- 

0-3097 

0-3165 

Hammered  Bessemer  iron  from  Hogbo  — 

32 

f      Marked  with  the  old  No.  of  hardness  5,  \ 
(         the  bar  No.  5  in  Table  LV  J 

7'879:1 

0-15 

- 

- 

- 

0-3476 

0-3473 

4 

Rolled  Bessemer  steel  from  Carlsdal— 

— 

0-99 

— 

Square. 

0-4651 

- 

- 

Rolled  puddled  steel  from  Surahammar— 

5 

Marked  N  i,  the  bar  No.  9  in  Table  LV 

7-828 

0-56 

— 

— 

— 

0-3629 

0-4029 

62 

B  i,  the  bar  No.  8  in  Table  LV. 

7-781 

o'66 

— 

— 

— 

0-3469 

0-3474 

7 

P  i     

— 

— 

0-7 

Square. 

0-4651 

— 

— 

Rolled  puddled  iron—- 

8 

From  Low  Moor    

7-780 

— 

0'2 

Round. 

0'5 

— 

— 

9 

From  Middlesbrough-on-Tees    

— 

— 

0-97 

Ditto. 

0-6162 

- 

- 

(  The  stem  of  a  rail  from  Cwm  Avon  in  ^ 

10 

\      Wales,  cut  out  by  a  planing  machine,  \ 
(.     and  heated  and  rolled  to  a  bar  j 

/•597 

!*~ 

— 

0-4523 

0-5009 

Rolled  puddled  iron  — 

ii2 

From  Motala.The  bar  No.  14  in  Table  L\ 

7-734 

— 

0'2 

— 

— 

0-3238 

0-3251 

12 

f      From  Surahammar,  marked  N.    The  \ 
t         bar  No.  15  in  Table  LV  J 

7-789 

0-14 

•  — 

- 

- 

O^ 

0-4702 

I32 

f      From  Surahammar,  marked  N  H.  The) 
\         bar  No.  16  in  Table  LV  j 

7-807 

- 

0-2 

- 

- 

Q'3473 

0-3483 

Rolled  iron  made  in  charcoal-hearth  — 

14 

From  Ayrd.  The  bar  No.  17  in  Table  LV 

7-780 

— 

O'l 

— 

— 

0-45I3 

0-4533 

15* 

18 

7-761 

— 

O'l 

— 

— 

0-4791 

0-4690 

16 

f     From  Hallstahammar.  The  bar  No.  19  ) 
t         Table  LV  j 

7-829 

- 

O'O7 

- 

- 

0-4052 

0-4520 

I72 

f      From  Hallstahammar.   The  bar  No.  20  ) 
t         Table  LV  j 

T*, 

— 

o-o, 

— 

— 

0-4263 

0-4584 

:.    REMARKS. — The  bars  Nos.  i,  2,  and  3  were  not  ordered  from  H6gh..>,  but  were  bought  in  Stockholm. 

The  bar  No.  2,  which  after  annealing  gave  a  modulus  of  elasticity  of  30,535,900  Ibs.,  on  stretching  was 
tested  by  bending  in  two  directions  at  right  angles  to  each  other.  The  modulus  of  elasticity  was  31,908,300168. 
in  the  one  case,  and  31,565,200  Ibs.  in  the  other.  The  bar  was  again  annealed,  but  the"  modulus  was  not 
increased  to  more  than  32,388,640  Ibs.  per  sq.  in. 

1  The  specific  gravity  was  taken  when 

2  The  bars  Nos.  2,  3,  6,  n,  13,  15,  and  17,  had  been 

3  By  annealing,  the  specific  gravity 


THE  MODERN  STEAM  BOILER. 


293 


MODULUS  of  ELASTICITY  in  Iron  and  Steel  by  FLEXION. 
each,  the  distance  between  the  supports  being  4  feet. 


The  modulus  of  elasticity. 


When  the  bar 
hud  not  been 
heated. 

Ihs.  per 
sq.  inch. 

When  the  bar 
had  been 

heated. 

De- 
crease 
by  the 
per- 
manent 
deflec- 
tion of 
the  bar. 

The  perman- 
ent deflection 
which  the 
bar  had 
obtained 
immediately 
before.1 

in. 

De- 
crease 
through 
harden- 
ing. 

De- 
crease. 

per 
cent. 

Bv  increase  in 
the 
temperature. 

Average 
diminu- 
tion by  an 
increase 
of  tem- 
perature 
of  1-8" 

F.=B,. 

In- 
crease. 

By  reduction 
of  temperature. 

Average 
increase 
by  reduc- 
tion of 
tempera- 
ture of  i  -8° 
^  =  8.. 

From 

To 
Fahr. 

From 

To 

Ibs.  per 
sq.  inch. 

per 
cent. 

per 

cent. 

Fahr. 

per  cent. 

per 
cent. 

Fahr. 

Fahr. 

per  cent. 

30.760,346 



I  "55 

0-1476 

ro 

1-98 

+  59 

+  266 

0'017 

0-64 

+  57 

0 

O'O2O 

— 

31,908,300 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

- 

— 

32,388,640 

— 

— 

- 

— 

— 

— 

— 

— 

— 

— 



- 

- 

- 

- 

3-2 

- 

- 

— 

- 

I-I2 

+  57 

+  2 

0-036 

29,232,120 

30,741,760 
30,673,140 

_ 

— 

ri 
r6 

3-28 
2-18 

+  51 
+60 

+  269 

+  257 

O'027 
O'O2O 

1-44 
I  '2O 
0-48 

+  57 
+59 
+  50 

+  2 
—  2 
+  14 

0-046 
0-035 
0-024 

— 

- 

— 

— 

— 

- 

— 

— 

- 

0'95 
I  -O2 

+66 
+60 

+  9 

+5 

0-030 
0-033 

27,310,160 

27,379,380 

— 

- 

— 

- 

- 

- 

-- 

i  '33 

+66 

+5 

0-040 

_ 

29,849,700 

— 

— 

— 

_ 

_ 

— 

— 

1-14 

+66 

o 

0-031 

30,810,380 

30,810,380 

1-88 

0-4476 

— 

2-60 

+  57 

+  273 

OX>22 

0-96 

+  55 

—  2 

0-030 

- 

31,839,680 

— 

— 

— 

- 

—   ' 

— 

— 

0-99 

+66 

+  11 

0-032 

27.585,240 

27,585,240 
27,516,620 

I  "47 

0-O8I3 

- 

4-06 

+57 

+  260 

0-036 

1-18 

+57 

+  2 

0-038 

31,084,860 

31,290,720 

070 

0-7034 

- 

- 

- 

- 

- 

I'll 

+66 

0 

0-030 

30,398,660 

— 

— 

— 

— 

— 

—  ' 

— 

— 

— 

- 

The  bar  No.  13  was  bent  throughout  the  whole  of  it's  length,  and  straightened  again.  The  modulus  cf 
elasticity  was  thus  decreased  6-6  per  cent. 

The  modulus  of  elasticity  of  the  annealed  bar  No.  15  on  flexion  was  first  27,379,350^5.,  and  by  repeat*  d 
annealing  did  not  increase  to  more  than  27,516,620  Ibs.  per  sq.  in. 


he  bars  were  in  their  original  state. 

icated  immediately  before  the  experiments. 

vas  increased  to  7-882. 


294 


THE  PRACTICAL  PHYSICS  OF 


W.  Parker's  Experiments. — During  the  year  1880  a  series  of 
tensile  tests  of  English  and  German  steel  at  various  temperatures 
was  carried  out  under  the  direction  of  Mr.  Wm.  Parker,  then 
chief  engineer-surveyor  of  Lloyd's  Registry  of  Shipping,  by 
whom  the  results  were  communicated  to  the  present  author. 

The  results  are  given  in  the  following  Table  : — 

TABLE  LVII. 


Temperature. 
Fahr. 

Stress  in  Tons  per  square  inch. 

Elongation  per  cent. 

English. 

German. 

English. 

German. 

70° 

31-5 

30-3 

I87 

I67 

450° 

357 

3Q-2 

I4-5 

I0'2 

610° 

32-0 

34'4 

I2'5 

I3'2 

1,000° 

i3'8 

117 

3-0* 

24-2 

*  Broke  close  to  the  end. 

In  these  experiments  the  tenacity  increased  as  the  tempera- 
ture rose  from  70°  to  450°,  whilst  the  ductility  diminished,  but 
between  450°  and  1,000°  both  rapidly  fell  away,  except  in  the 
case  of  the  German  steel,  which  showed,  on  the  contrary,  an 
increase  of  ductility. 

Kollmann's  Experiments, — Following  these  tests,  as  to  date  of 
publication  in  this  country,  but  rivalling  in  completeness  those  of 
Professor  Styffe,  there  is  the  series  of  experiments  carried  out  by 
Dr.  J.  Kollmann  at  the  works  of  theGutehoffnungshutte,  nearOber- 
hausen,  the  results  of  which  \vere  communicated  by  him  to  the 
Verhandlungen  des  Vereins  zur  Beforderung  des  Gewerbfleisses 
(1880,  p.  92).1 

Illustrations  of  the  testing  machines  and  test  pieces  employed 
will  be  found  in  Engineering  of  February  4th,  1881.  In  all 
the  tests  made,  only  ordinary  iron  as  daily  produced  and  used 
at  the  Gutehoffnungshutte  was  employed,  it  being  the  object  of 
the  experiments  to  determine  the  behaviour  of  such  iron  as  the 
Works  ordinarily  made.  Fibrous  iron,  fine-grained  iron,  and 


1  An  abstract  of  this  paper  is  published  in  Engineering  of    Feb.  4,  1881, 
p.  109.     See  also  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixxxiv.,  p.  417. 


THE  MODERN  STEAM  BOILER.  295 

Bessemer  steel  were  tested,  their  relative  specific  gravities  being 
7-62,  7-69,  and  7*84.  The  test  pieces  used  in  the  smaller  machine 
were  all  13  mm.  (0-51  inch)  in  diameter,  or  13  mm.  square,  and 
in  the  larger  machine  40  mm.  by  10  mm.,  or  1-58  by  0^39  inch, 
say  0*6201  square  inch.  Careful  measurements,  both  before  and 
after  the  tests,  were  made  by  means  of  micrometers.  The 
following  gives  the  chemical  composition  of  the  three  qualities 
used  :— 

TABLE  LVIII. 


Weldable  wrought 

Fine  grained 

Iron. 

Iron. 

Bessemer  Steel. 

Carbon 

O'lO 

O'I2 

0-23 

Silicon 

0-09 

O'll 

0-30 

Phosphorus 

0-34 

O'2O 

0-09 

Sulphur 

°'°3 

trace 

0-05 

Manganese 

0-07 

0-14 

0-86 

Copper 

0-07 

0-06 

0-07 

Iron 

99-30 

9936 

98-40 

loo'oo  99'99  loo'oo 

Special  means  were  adopted  for  heating  the  test  pieces,  and  a 
second  test  piece  of  the  same  quality  of  iron  was  always  heated 
along  with  the  one  put  in  the  testing  machine,  so  that  this 
second  piece  should  be  used  for  measuring  the  temperature  of 
each  experiment  by  means  of  a  calorimeter.  No  correction 
was  considered  necessary  to  allow  for  any  water  lost  by  evapora- 
tion during  an  experiment,  or  for  losses  by  radiation.  The 
calorimeter  was  so  well  protected  against  radiation  that  in  a  trial 
extending  over  two  hours  there  was  a  loss  of  only  ri°  C.,  the 
temperature  of  the  air  being  21*2°  C. 

Experiments  were  made  to  determine  the  rate  of  cooling  of 
small  test  pieces  40  mm.  by  10  mm.  in  section,  and  the  results 
are  plotted  in  the  curve  in  Fig.  123,  the  horizontal  .divisions  giving 
the  time  in  minutes,  and  the  vertical  ordinates  the  temperature 
in  degrees  C.  Similar  experiments  were  made  with  the  larger 
test  pieces,  13  mm.  diameter  by  280  mm. -long,  and  their  curve 
of  decrease  of  temperature  is  shown  in  Fig.  124. 

With  regard  to  the  regular  experiments,  a  Table  was  given 
containing  the  results  of  52  tests,  showing  the  effects  of  rise  of 


296 


THE  PRACTICAL  PHYSICS  OF 


temperature  in  reduction  of  resistance  to  rupture,  and  in  increase 
of  the  contraction  of  sectional  area,  as  well  as  increase  of  ex- 
tension. On  account  of  the  rapidity  with  \vhich  the  test  pieces 
cooled  it  was  found  impossible  to  make  accurate  observations  at 
a  higher  temperature  than  1080°  C.  (1976°  F.),  and  for  this  reason 
Dr.  Kollmann  recommends  that  future  experiments  should  be 
made  with  test  bars  of  larger  diameter,  which  wrould  retain  their 
heat  longer.  Taking  the  initial  strength  as  37-5  kilos,  per  square 
millimetre  or  23-81  tons  per  square  inch  at  o°  C.,  and  calling  this 
breaking  load  100,  the  progressive  diminution  in  resistance  to 
rupture  is  thus  shown  : — 

TABLE  LIX. 


Degrees  Centigrade. 

Fibrous  Iron. 

Fine  Grained  Iron. 

Mild  Bessemer  Steel. 

0 

100 

IOO 

IOO 

100 

IOO 

IOO 

IOO 

200 

95 

IOO 

IOO 

300 
400 
500 
600 
700 

90 

73 
38 
19 
16 

97 

44 

94 

34 
18 

23 

800 

ii 



—  — 

900 

6 

12 

9 

1,000 

2,250 

4 
o 
Broke    without 
appreciable  load 

7 

7 

That  is  to  say,  at  a  temperature  of  200°  C.  the  breaking  load  in 
the  case  of  the  fibrous  iron  was  reduced  to  22 -6  tons,  or  95  per 
cent,  of  the  initial  load  ;  at  300°  C.  to  21-4  tons  ;  at  400°  C.  to 
17*39  tons  ;  at  500°  C.  to  9*14  tons  ;  at  600°  C.  to  3-94  tons  ;  at 
800°  C.  to  2-54  tons  ;  at  1000°  C.  to  0*05  ton  ;  whilst  at  2250°  C. 
the  iron  broke  without  any  appreciable  load.  These  results  and 
the  corresponding  ones  with  the  other  two  qualities  of  iron 
tested  are  given  graphically  in  the  following  curves  (Figs.  125, 126, 
127),  the  melting  temperature  of  wrought  iron  being  assumed  at 


THE  MODERN  STEAM  BOILER. 


\ 


\ 


FIG.   123. 


FIG.   124. 


FIG.   125. 


t  it'll  tint  I'M  in 


FIG.    126. 


0 II 


it 


FIG.    127. 


298  THE  PRACTICAL  PHYSICS  OF 

2250°  C.  (4082°  F.)  according  to  Dr.  Wedding.  The  results 
shown  by  these  curves  up  to  about  1100°  C.  (2012°  F.)  are  fairly 
accurate,  but  beyond  that  temperature  it  was  most  difficult  to 
obtain  reliable  readings.  Up  to  about  450°  C.  (842°  F.)  there 
was  an  increase  in  the  extension  as  well  as  in  the  reduction  of 
sectional  area,  which  continued  in  the  latter  case  up  to  600°  C., 
whilst  the  extension  decreased.  Between  600°  C.  and  700°  C. 
(1112°  and  1292°  F.)  the  contraction  decreased,  but  above  700°  C. 
it  increased  again.  The  extension  also  increased  between 
700°  C.  and  850°  C.  (1292°  and  1562°  F.),  but  from  this  point  it 
very  rapidly  decreased. 

From  a  number  of  experiments  the  elastic  limit  was  deter- 
mined for  750°  C.  (1382°  F.)  to  be  2-30  tons  per  square  inch, 
at  800°  C.  (1472°  F.)  1-27  ton,  and  at  850°  C.  (1562°  F.)  to  be  0-95 
ton  per  square  inch. 

Subsequently  some  experiments  were  made  with  predetermined 
loads  in  order  to  test  the  reduction  of  sectional  area  and  the 
extension  at  given  temperatures.  The  temperatures  ranged 
between  460°  and  700°  C.  (860°  and  1292°  F.),  the  loads  at  these 
temperatures  respectively  being  in  tons  per  square  inch  2 '86  and 
2*35.  The  reductions  of  sectional  area  were  7*5  and  40^83  per 
cent.,  and  the  elongations  4-5  and  22  percent.  Figs.  126  and  127 
show  graphically  the  results  with  the  other  qualities  of  iron  used. 

These  tests  were  combined  with  an  investigation  of  the  tem- 
peratures at  which  iron  is  rolled,  and  of  its  behaviour  under  the 
action  of  rolling,  in  order  to  obtain  a  basis  for  a  theory  of  rolling 
mills.  This  investigation,  although  interesting,  has  only  an  indirect 
application  to  our  subject,  inasmuch  as  it  revealed  that  the 
strength  of  bars  was  to  some  extent  increased  by  the  amount  of 
work  and  compression  to  which  they  were  subjected.  This, 
however,  has  a  limit,  because  the  experiments  of  Pisati  and 
others  on  the  extension  of  heated  iron  and  steel  wire  under 
different  loads  and  at  different  temperatures  from  32°  to  572°  F. 
(o°  to  300°  C.)  gave  discordant  results. 

Pisati's  Experiments  with  Wire. — Pisati  found  that  with  un- 
annealed  wire  the  extension  is  very  small,  and  decreases  with 
the  rise  of  temperature.  It  was  observed  that,  in  a  wire  cooled 
at  a  dark  red  heat,  the  strength  decreased  between  57°  and  122° 
F.,  but  increased  from  that  point  up  to  194°  ;  decreased  again  up 
to  248°,  remaining  then  constant  up  to  392%  and  then  slowly 


THE  MODERN  STEAM  BOILER.  299 

decreasing  to  455°  F.,  when  it  suddenly  commenced  to  increase, 
after  which  a  slow  decrease  in  strength  set  in.  It  must  be 
remarked,  however,  that  the  strength  at  572°  was  greater  than  at 
57°.  The  extension  decreased  between  57°  and^  167°,  and  then 
increased  up  to  212°,  again  decreasing  rapidly  to  257°,  when  the 
variation  disappeared,  and  the  extensibility  remained  constant  up 
to  437°.  Again  it  increased  quickly,  subsequently  more  slowly 
until  at  572°  it  was  the  same  as  at  57°  F.  This  irregularity  was 
quite  absent  in  the  case  of  Dr.  Kollmann's  tests  of  iron  and 
steel  plate. 

Effect  of  High  Temperature  on  Steel. — Again,  steel  being  a  material 
capable  of  being  fused,  it  is  found  that  it  cannot  be  wrought 
at  so  high  a  temperature  as  that  which  malleable  iron  stands 
without  any  damage,  and  that  as  the  temperature  of  fusion  is 
approached  steel  suffers  in  strength  and  ductility,  becoming 
what  is  technically  termed  "  burned."  It  probably  forms  some 
union  with  oxygen  such  as  does  Bessemer  steel  when  overblown, 
because  by  careful  manipulation  its  good  qualities  can  be  to  a 
great  extent  restored. 

Effect  of  Low  Temperature  on  Steel. — On  the  other  hand  it  is 
dangerous  to  put  work  upon  steel  plates  or  bars  at  too  low  a 
heat,  and  careful  investigations  have  shown  that  when  worked, 
by  rolling,  bending,  or  hammering,  at  a  blue  heat  or  about  250°  F. 
permanent  injury  is  done  to  the  strength  of  the  material, 
and  internal  stresses  are  set  up  which  have  produced  the 
mysterious  fractures  so  puzzling  to  engineers  and  shipbuilders 
in  the  early  days  of  the  introduction  of  that  material  in  the  con- 
struction of  boilers.  The  presence  of  a  comparatively  high 
percentage  of  carbon  and  a  tensile  strength  of  29  to  32  tons  per 
square  inch  are  factors  in  the  production  of  the  injurious  effects 
of  a  blue  heat,  although  steel  of  a  less  tensile  strength,  and  even 
wrought  iron,  may  suffer  from  it.  This  matter  was  carefully 
inquired  into  in  consequence  of  some  trouble  with  the  thick 
steel  plates  required  for  steam  boilers  of  large  diameter  for  high 
pressures,  and  full  accounts  of  experiments  will  be  found  in 
Trans,  of  the  Inst.  of  Naval  Architects,  Vols.  xix.,  pp.  172-192  ; 
xxvi.,  pp.  253-277  ;  xxvii.,  pp.  67-150  ;  and  Min.  Proc.  Inst. 
C.  E.,  Vol.  Ixxxiv.,  pp.  114-207  ;  xcviii.,  147,  etc.1 

1  See  also  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixix.,  35  ;  lx.,  219  ;  Ixxxviii.,  463  ;  Tracts, 
Folio  Vols.  29-32  ;  Proc.  Inst.  Mechanical  Engineers,  1880,  p.  225. 


300  THE  PRACTICAL  PHYSICS  OF 

Water-tube  boilers  are  to  a  great  extent  removed  beyond 
danger  from  this  source,  because  they  are  under  no  necessity  to 
employ  thick  plates  in  their  construction,  and  it  has  been  found 
that  the  chance  of  damage  to  their  plates  or  tubes  from  the 
above  cause  is  -extremely  small. 

Professor  Martens'  Report. — Further  investigations  were  com- 
menced in  1886,  under  the  auspices  of  two  German  technical 
societies,  the  Verein  zur  Beforderung  des  Gewerbfleisses  of 
Berlin  and  the  Verein  Deutscher  Eisenhiittenleute  of  Dusseldorf, 
and  were  reported  upon  by  Professor  Martens l  in  Mittheilungen 
aus  den  Koniglichen  technischen  Versuchsanstalten  zu  Berlin 
(No.  iv.,  Vol.  viii.,  1890,  page  159).  It  was  considered  that 
previous  experiments  had  not  been  sufficiently  uniform  and 
exhaustive,  especially  with  iron  and  steel  up  to  a  temperature,  of 
600°  C.,  and  consequently  a  systematic  series  of  experiments 
was  decided  upon.  It  was  intended  to  subject  to  the  tests  four 
qualities  of  mild  steel  having  a  tensile  strength  of  22*86,  26-67, 
30-48  and  34*28  tons  per  square  inch  in  their  annealed  condition, 
but  the  material  furnished  for  the  last  or  fourth  group  of  tests 
was  found  to  be  not  up  to  the  required  standard,  and  therefore 
only  three  qualities  were  tested.  Carefully  formed  and  annealed 
test  pieces  were  prepared,  and  all  necessary  precautions  wrere 
taken  to  have  the  temperature  and  other  readings  correct. 
Special  apparatus  was  used  for  both  cold  and  hot  tests  ;  in  the 
latter  case  the  test  pieces  were  kept  at  the  required  temperature 
during  test  by  being  immersed  in  melted  paraffin,  for  tempera- 
tures up  to  200°,  or  in  melted  alloys  of  lead  and  tin,  or  of  lead 
only,  for  temperatures  up  to  600°  C. 

A  description  of  the  testing  machine  was  published  in  the 
Zeitschrift  des  Vereins  deutscher  Ingenieure,  1886,  p.  171,  and 
Mittheilungen  aus  den  Technischen  Versuchsanstalten  of  1889, 
Supplementary  No.  iii. 

"  In  ordinary  tests  \vith  the  machine  employed  for  these 
experiments  no  measurements  are  taken  between  the  moment 
when  the  maximum  load  is  reached  and  the  final  fracture.  In 
the  present  case,  however,  it  was  thought  desirable  to  observe 
more  accurately  the  phenomena  occurring  between  maximum 
load  and  fracture,  since  it  was  evident  beforehand  that  at 

1  See  abstract  in  Min.  Proc,  Inst.  C.E.  Vol.  civ.  209-224. 


THE  MODERN  STEAM  BOILER. 


301 


different  temperatures  very  considerable  differences  in  the 
behaviour  of  the  metal  during  this  period  would  show  them- 
selves. 

"  For  observing  the  decreasing  tensile  strength  of  a  test  piece 
the  automatic  recorder  on  the  left  side  of  the  testing  machine 
was  employed.  The  course  of  the  experiment  was  generally 
as  follows  :  The  test  piece,  after  accurate  measurement  of  all 


FIG.   128. 


parts,  was  pushed  from  below  into  the  furnace,  and  a  tight 
joint  made  by  means  of  the  conical  shoulder  smeared  with  fine 
clay  ;  the  test  piece  and  furnace  were  then  firmly  connected  by 
a  nut.  The  iron  tube  (filled  with  nitrogen)  of  the  air  ther- 
mometer was  next  placed  inside  the  furnace,  the  measuring  rods 
of  the  mirror  apparatus  were  attached,  and  finally  the  stirring 
mechanism  and  cover.  After  the  test  piece  had  been  fixed  in 
the  spherical  bearings  of  the  testing  machine,  the  mirror 
apparatus  was  connected." 


302 


THE  PRACTICAL  PHYSICS  OF 


All  the  pieces  to  be  tested  at  high  temperatures  were  pre- 
viously tested  several  times  at  an  ordinary  temperature  as  to 
their  elastic  extension  within  the  limits  of  proportionality,  so 
that  the  extension  for  one  ton  (i.e.,  a  metric  tonne  =  0^9842  ton 
avoirdupois)  could  be  determined  with  great  accuracy  and  from 
this  the  modulus  of  elasticity.  After  these  preliminary  observa- 
tions the  gas-jet  was  lighted  and  the  furnace  gradually  heated. 
The  material  for  filling  the  inner  space  of  the  furnace  was 


FIG.    129. 

melted  and  poured  in  when  the  furnace  was  sufficiently  hot. 
The  temperatures  up  to  400°  C.  were  observed  by  means  of  a 
mercury  thermometer,  and  the  higher  temperatures  with  an  air 
thermometer.  At  450°  the  results  obtained  from  both  ther- 
mometers were  compared  and  graphically  recorded — special 
precautions  being  taken  to  neutralise  the  variations  of  the  air 
thermometers. 

u  The  main  results  are  given  in  a  tabular  form  in  the  original 
paper,  but  for  comparison  are  also  graphically  represented.     In 


THE  MODERN  STEAM  BOILER. 


303 


Figs.  128,  129,  and  130,  the  extension  differences,  corresponding 
to  the  various  loads,  are  shown  for  the  different  qualities  of  metal, 
I.,  II.,  and  III.,  and  the  various  temperatures.  These  diagrams 
allow  an  opinion  to  be  formed  of  the  degree  of  accuracy  obtained, 
and  also  on  the  question  as  to  how  far  the  material  can  be  credited 
with  a  proportional  extension.  From  the  decreasing  length  of 
the  parallel  portions  of  the  curve-groups  with  increasing  tempera- 
tures, the  lowering  of  the  limit  of  proportionality  is  plainly  visible 


.  i 


FIG.    130. 


Even  at  300°  it  appears  questionable  whether  the  test  pieces  can 
be  truly  said  to  show  any  proportional  extension. 

In  Figs.  131,  132,  and  133,  the  chief  results  are  delineated  for 
the  three  qualities  of  material.  The  quantity  represented  by  each 
curve  is  denoted  by  the  letters  at  the  commencement  of  each  on 
the  left  hand,  the  meaning  of  the  notation  being  as  follows  :— 

A  o  =  Percentage  of  elongation  per  ton  of  load. 

cs=  Percentage  of  elongation  per  limit  of  stretch,  or  limit  of 
elasticity,  i  c.,  yielding  point  where  flow  of  metal  commences. 


304 


THE  PRACTICAL  PHYSICS  OF 


E  o 

KGS  P.SQ. 


/ 

\L 


-20*20  /OO 


2SOOO  *«5 
RSQ  *»  M 

20OOO     O§ 


500  £00* 


200  30O  *00 

QUALITY  I. 

FIG.   131. 

^p=  Percentage  of  elongation  per  limit  of  proportionality,  or 
the  point  up  to  which  stress  and  strain,  accurately  measured, 
remain  proportional. 

E  =  Modulus  of  elasticity. 

q=  Contraction  of  area  in  per  cent. 

o-B=  Maximum  stress. 

£z=  Breaking  stress. 

£z=  Percentage  of  elongation  at  fracture. 

<rs=  Stress  at  limit  of  stretch. 


THK  MODERN  STEAM  BOILER. 


305 


200 

AS 


KGS  PSQ 
M  M 

60 


/ 


25000  KGS 
P.SQ  M.M 


15000 
£ 


-20*20  '00  700  300  400  5"0  60O< 

QUALITY  II. 

FIG.   132. 

CB= Percentage  of  elongation  at  maximum  load. 

flrp= Stress  at  limit  of  proportionality. 

oloo= Percentage  of  elongation  in  200  millimetres. 

The  elongations,  except  where  otherwise  stated,  are  referred 
to  the  test  length  of  206  millimetres. 

Figs.  131  to  133  show  very  clearly  how  the  stresses  o-B  and  o-z 
decrease  considerably  from — 20°  up  to  about  50°,  and  after  that 
rapidly  increase  until  they  attain  a  maximum  at  from  200°  to 
250°.  This  maximum  value  is  for  all  the  qualities  of  material 


3o6 


THE  PRACTICAL  PHYSICS  OF 


20  IOO  20O  3OO  *00  500  6OO 


FIG.    133. 

tested  considerably  in  excess  of  the  value  for  -f  20°  ,  and  by  the 
following  amounts  :  — 

Quality.  Excess  for  arK.  Excess  for  <rz. 

I.  ...         34  per  cent.         ...  62  per  cent. 

II.  ...         27     „       „  45     „      M 


III. 


5° 


The  curves  for  <rz  follow  a  similar  course.  On  comparing  the 
curves  for  <TB  and  <rz,  it  will  be  found  that  the  maxima  and 
minima  occur  at  nearly  the  same  temperatures.  The  following 


THE  MODERN  STEAM  BOILER. 


307 


are  the  ratios  of  0^  to  <TB  in  per  cent,  for  various  temperatures, 
as  calculated  from  the  mean  values  obtained  : — 

TABLE  LX. 


Quality  <>t 
Material. 

Ratio  for 

-20° 

+  20°               100° 

200° 

300° 

4oo° 

500° 

fXX)° 

I. 

76 

75           77 

£6 

96 

66 

39 

12 

II. 

as 

82           85 

92 

96 

76 

43 

7 

III. 

7 

74          79 

91 

96 

84 

49 

16 

With  the  exception  of  some  of  the  test  pieces  of  quality  III. 
the  material  which  is  strongest  in  a  cool  state  remains  so  when 
heated. 

The  diagrams  (Figs.  134  and  135)  allow  a  comparison  of  the 
leading  results  for  all  three  qualities  of  material  tested. 

In  general  No.  III.  exhibits  the  same  characteristics,  as  regards 
the  values  of  <TB  and  <rz,  as  the  other  two,  but  deviates  notably 
from  the  latter  at  300°.  The  elongation  CB  increases  between 
—  20°  and  +20°,  and  then  for  I.  and  II.  decreases  and  reaches 
a  minimum  at  about  130°.  From  this  point  the  curves  rise 
again  up  to  between  280°  and  330°,  and  then  fall. 

For  No.  III.  the  minimum  value  of  £B  is  reached  only  at  300°, 
and  the  curve  afterwards  rises,  a  maximum  occurring  at  4OO°t 
Similar  differences  are  also  to  be  observed  in  the  character  of 
the  curves  for  cz. 

The  following  Table,  compiled  from  the  mean  observed 
values,  gives  the  ratios  in  per  cent,  of  CB  to  cz,  for  various 
temperatures  : — 

TABLE  LXI. 


Quality  of 
.Material. 


Ratio  for 


-20° 

+  20° 

100° 

200° 

300° 

400° 

500° 

600° 

I. 

78 

76 

76 

79 

73 

36 

20 

[28J 

II. 

75 

79 

68 

76 

81 

58 

19 

8 

III.        78 

72 

81            74 

59           48 

26 

15 

308 


THE  PRACTICAL  PHYSICS  OF 


t/ol 


8         9 


O?      d 

SI 
I 


i        i 


\ 


</    / 


THE  MODERN  STEAM  BOILER.  309 

In  Fig.  136  the  stress  diagrams  for  material  of  quality 
No.  II.  are  reproduced.  The  limit  of  stretch  in  each  diagram 
is  denoted  by  S,  the  point  of  maximum  stress  by  B,  the  point  of 
fracture  by  Z.  At  400°  the  material  assumed  the  character  of 
the  soft  metals,  such  as  zinc.  The  irregularities  at  the  points  a 
and  6  occurred  when  the  flow  extended  to  the  shoulders  of  the 
test  pieces,  beyond  the  actual  test  length. 

The  variations  in  the  contraction  of  area  were  extraordinarily 
great.  For  all  three  qualities  the  smallest  value  of  <?,  the  reduc- 
tion of  area,  occurs  at  300°. 

The  stress  at  the  limit  of  proportionality  increases  with  rising 
temperature  between  —  20°  and  +20°,  reaching  a  maximum 
about  +20°  ;  it  then  falls  slightly  to  100°,  and  at  200°  attains  a 
second  higher  maximum,  subsequently  falling  rapidly.  The 
elongation  at  the  limit  of  proportionality  3P,  is  subject  to  no 


•"•20°    6OO"+20*  IOO*          100*   too- 100- too- 

FIG.   136. 


appreciable  alterations.  For  the  stresses  usual  at  ordinary 
temperatures  the  engineer  may  therefore  reckon,  in  steel  heated 
even  up  to  200°,  on  elongations  proportional  to  the  load  and  on 
sufficient  safety.  It  would,  however,  scarcely  be  safe  to  draw 
conclusions  from  the  results  of  these  experiments  as  to  the 
admissible  working  stress  for  temperatures  above  200°,  or  for 
frequent  changes  of  temperature  ranging  from  150°  to  350°. 
Reliable  values  in  such  cases  could  only  be  arrived  at  by 
repeated  tests,  continued  for  long  periods,  with  the  metal  in  a 
heated  state. 

The  question  of  the  safety  of  iron  structures  may  be  influenced 
by  the  peculiar  behaviour  of  the  material  at  300°.  At  this 
temperature  the  strength  is  greater,  but  the  reduction  of  area  and 
elongation  are  less  than  in  a  cold  state.  Fracture  occurs 
suddenly  without  previous  contraction,  the  metal  exhibiting  a 
certain  brittleness,  which  also  rinds  expression  in  the  appearance 


310  THE  PRACTICAL  PHYSICS  OF 

of  the  fractured  surface.  On  this  account  it  is  questionable 
whether  at  300°  steel  is  capable  of  resisting  repeated  shocks." 

A  further  series  of  experiments  on  wrought  iron,  mild  steel, 
copper,  delta-metal,  and  manganese  bronze,  by  M.  Rudeloff,  is 
reported  in  the  same  paper1  which  had  previously  published 
M.  Martens'  results,  but  these  experiments  do  not  call  for  special 
notice. 

Whilst,  however,  wrought  iron,  Siemens  steel,  copper,  and 
delta-metal  all  proved  to  be  comparatively  or  wholly  unsafe 
under  stresses  at  temperatures  above  250°  C.,  manganese  bronze 
proved  to  be  very  little  affected  by  heat,  so  that  it  could  be 
safely  used  at  250°  C. 

M.  Rudeloff  also  carried  out  experiments  at  the  Imperial 
Navy  Yard,  Wilhelmshaven,  on  the  strength  of  iron  and  steel 
at  low  temperatures,  but  these  do  not  specially  bear  upon  our 
subject. 

Professor  Carpenter's  Tests. — Professor  Carpenter  -  has,  however, 
recently  carried  out,  at  Sibley  College,  Cornell  University,  tests 
on  the  effects  of  both  decrease  and  increase  of  temperature  on 
tensile  strength  and  has  carried  the  latter  to  a  higher  point 
than  usual. 

The  general  results  show  first  a  decided  increase  in  strength, 
accompanied  by  a  corresponding  rise  in  the  strength  at  elastic 
limit,  as  the  temperature  is  lowered — the  latter,  however,  not 
being  so  well  marked.  The  percentage  of  elongation  remains 
essentially  constant  and  so  does  the  modulus  of  elasticity  at  all 
temperatures  from  -f  70°  to  —  60°  F. — the  range  of  the  tests.  Some 
previous  tests  on  wrought  iron  and  steel  at  high  temperatures 
showed  a  decided  increase  in  strength  as  the  temperature 
increased  from  70°  to  about  500°  F.,  after  which  the  strength 
rapidly  diminished.  A  combination  of  these  experiments  would 
seem  to  show  that  the  strength  of  wrought  iron  increases  with 
the  change  in  temperature  from  about  70°  F.  in  either  direction, 
and  that  the  change  is  well  marked,  of  considerable  amount,  and 
is  characteristic  of  all  specimens. 

1  Mittheilungen    aus  den   Koniglichen   Versuchsanstalten  /u    Berlin,    1893, 
p.   292  ;   see   also  Stahl   und   Eisen,    1890,    p.    607  ;  Min.    Proc.    Inst.    C.E., 
Vol.  cxvii.,  p.  461. 

2  Published  in  the  issue  for  1898  of  "  The  Technic,"  by  the  University  of 
Michigan    Engineering   Society.      See   also   the    Railroad    Gazette   and   the 
Mechanical  P^ngincer,  November  26th,  1898. 


THE  MODERN  STEAM  BOILER.  311 

Fig-  *37  is  a  com bined  diagram  showing  the  results  of  the  tests 
made  both  at  low  and  at  high  temperatures.  In  plotting  this 
diagram,  the  strength  in  both  series  of  tests  was  equalised  to  a 
common  starting  point  at  70°  F.  so  as  to  make  the  curve 


*. 

«^, 

**  ^4— 

^  ?       ^ 

^ 

*  * 

^ 

—       S*.         .,    ^r< 

s 

ft 

50 

Temperature  ot  Te»t  Specimen   Qeqree»  Fohrenhrii. 
Fill. 


continuous.    This  in  result  may  not  be  true,  but  the  strict  record 
would  only  show  the  curve  of  strength  for  the  higher  tempera- 
tures in  a  position  slightly  above  the  one  showrn.     The  material 
in  both  series  of  tests  was  as 
nearly    uniform     as     possible, 
although  some  years  intervened 
between  the  two  series.     The 
material  tested  at  high  tempera- 
tures was  slightly  stronger  than 
that  used  in  the  low-tempera- 
ture tests. 

In  Fig.  138  are  given  the 
curves  of  tests  of  wTOught  iron, 
machinery  steel,  and  tool  steel, 
at  high  temperatures.  The 
similarity  of  the  form  of  the 
curves  for  different  materials 
shows,  so  far  as  the  points  of 
maximum  and  minimum  indi- 
cate, that  the  nature  of  the 
material  has  little  effect  on  the 

general  character  of  the  relation  of  strength  to  change  of 
temperature,  and,  further,  that  the  strength  is  greatly  affected 
by  the  temperature. 

Fig.  139  shows  the  elongation   in  specimens  eight  inches    in 


KK)    too    500    400    500    600  700    80C 

Temperature  of  the  Specimen. 
FIG.  138. 


312  THE  PRACTICAL  PHYSICS  OF 

length  of  wrought  iron  and  tool  steel  at  different  temperatures. 
The  elongation  decreases  at  first  with  rise  of  temperature  until  a 

minimum  is  reached  at  about 
250°  F.,  after  which  it  increases 
with  the  temperature. 

An  interesting  comparison  of 
the  results  with  cast  iron  is 
afforded  by  Fig.  140,  which  gives 
the  results  of  tests  with  that 
material.  The  tensile  strength  of 
cast  iron  remained  practically 
uniform  from  a  temperature  of 
70°  to  nearly  700°  F.,  but  from 
that  point  it  decreased  in  rapid 
proportion  to  the  increase  of 
temperature,  becoming  practically 
nil  at  1240°  F.  The  elongation 
per  inch  in  length  appeared  to  decrease  slightly  from  100°  to 
400°,  after  which  it  increased  with  rise  of  temperature  to  1200°. 
The  elongation  of  cast  iron  is  so  small  under  the  best  conditions 
that  it  has  little  importance  beyond  that  belonging  to  scientific 


100  300  £OO  700 

Temperature  of  the  Specimen. 


FIG.  139. 


100    200    300   400    500    600  JOO    80O    900    1000    1100    l£00    1500 

Temperature  in  Deqrees  Fahrenheit. 
Effect  of  Temperature  on  Strength  of  Cast  Iron, 
FIG.  140. 

interest.     The    tests,  however,  indicate    a    brittle    condition   at 
about  300°  or  400°  F. 

Professor  Carpenter  discussed  the  question  of  the  production 


THE  MODERN  STEAM  BOILER. 


313 


of  crystalline  fractures,  and  both  his  report  and  that  of  Professor 
Martens  (already  alluded  to)  should  be  consulted  for  details  of 
that  branch  of  the  inquiry.  The  more  recondite  side  of  the 
investigation  into  the  molecular  changes  in  iron  and  steel  at  high 
temperatures  will  be  found  in  the  writings  of  Barrett  (Phil. 
Magazine,  Vol.  xlvi.,  p.  472),  Pionchon,  and  Le  Chatelier 
(Comptes  Rendus  de  1'Academie  des  Sciences,  Vol.  cii.,  pp.  670, 
1454),  and  Osmond  (Comptes  Rendus,  vol.  ciii.,  p.  743).' 

Strength  of  Copper  and  Alloys. — Investigations  into  the  effects  of 
high  temperatures  on  the  strength  of  copper  and  of  various  alloys 
have  also  been  made  ;  and  as  many  of  these  materials  may  be  used 
for  boiler  fittings  or  accessory  apparatus,  the  results  have  more 
or  less  connection  with  our  subject. 

We  have  seen  that  at  the  temperature  corresponding  to  a 
steam  pressure  of  200  Ibs.  per  square  inch,  viz.,  about  388°  F.  or 
215°  C.,  the  strength  of  wrought  iron  or  steel  is  not  much  affected, 
and  in  fact  that  it  increases  till  some  point  between  350°  and 
540°  F.  is  reached.  At  the  same  time  the  ductility  has  decreased, 
and  if  the  metal  is  steel  which  has  been  worked  at  a  blue  heat, 
there  might  be  serious  consequences.  Apart  from  that  both 
wrought  iron  and  steel  should  be  reliable  at  even  the  highest  of 
these  temperatures.  "  With  copper  and  its  alloys,"  we  are 
informed,  "  a  very  different  state  of  affairs  obtains.  The  steam 
pipes  which  proved  perfectly  reliable  with  steam  of  80  Ibs. 
pressure  and  a  temperature  of,  say,  324°  F.,  have  proved  much 
less  satisfactory  when  this  pressure  has  been  doubled,  though 
this  has  involved  an  increase  in  the  temperature  of  only 
about  37°  F.  Careful  laboratory  experiments  have  conclusively 
established  the  fact  that,  under  certain  conditions,  copper  may 
suffer  a  serious  loss  of  strength  on  being  baked  for  a  prolonged 
period  at  a  temperature  of  400°  F.,  and  other  experiments  have 
shown  a  considerable  loss  of  strength  when  tested  at  still  lower 
temperatures.  Much  depends  on  the  condition  of  the  metal  to 
begin  with.  A  hard  copper  loses  proportionately  more  than  soft 
annealed  copper,  and  the  result  is,  perhaps,  also  dependent  on 
the  rate  at  which  the  load  on  the  specimen  is  applied  by  the 

1  Refer  also  to  Sir  W.  C.  Roberts-Austen's  papers  on  the  Measurement  of 
High  Temperatures,  in  Min.  Proc.  Inst.,  C.  E.,  Vols.  ex.,  etc.  ;  also  Journal  Iron 
and  Steel  Inst.  and  Trans.  Inst.  Mech.  Eng.  ;  also  to  Min.  Proc.  Inst.,  C.  E. 
Vols.  Ixxxvi,,  462,  andxci.,  544. 


3 14  THE  PRACTICAL  PHYSICS  OF 

machine.  Some  experiments  of  M.  Le  Chatelier  show  this  time 
effect  well.  They  were  made  with  some  specimens  of  copper 
wire  : — 

TABLE  LXII. 


Materi 


Strength  at  482°  Fahr.  when  the  Test  lasted. 


Strength    at 
60°  Fahr. 


Hard  Copper 
Soft  Copper 


inch. 


3175 
I5-9 


Ten  seconds.    I     Ten  minutes. 


Tons  per  square  Tons  per  square  Tons  per  square  Tons  per  square 


inch 


nch. 


21-6 


157 


Thirty  minutes. 


inch. 
I4'43 

10-4 


These  figures  show  the  great  influence  of  time,  and  possibly 
the  somewhat  discordant  results  obtained  by  different  observers 
may  here  find  an  explanation." 

"M.  Le  Chatelier  maintains  that  good  copper,  thoroughly 
annealed,  has  a  strength  of  not  more  than  10  tons  per  sq.  in., 
when  tested  at  a  temperature  of  400°  F.  Even  this  low  figure 
cannot  be  relied  on  in  the  case  of  steam  pipes  with  brazed  joints, 
as  the  quality  of  the  metal  is  often  seriously  injured  in  the  neigh- 
bourhood of  the  joint."  Small  quantities  of  impurities,  such  as 
Arsenic  or  Bismuth,  often  found  in  copper,  also  act  in  lowering 
the  strength  and  ductility  of  the  metal,  just  as  sulphur  and 
other  impurities  do  with  steel.  "  Coming  to  alloys,  many  of 
these  are  far  from  reliable  at  high  temperatures.  Different 
samples  of  gun-metal  show  widely  varying  results.  Some 
specimens  lose  rapidly  in  strength  as  the  temperature  is  raised, 
whilst  others,  in  particular  those  containing  phosphorus,  show 
much  more  favourable  results. 

"  Aluminium  bronze  in  the  rolled  state  also  preserves  its  strength 
well,  but  with  castings  the  results  are  less  favourable." 

Experiments  on  a  variety  of  alloys  were  made  at  the  instance  of 
the  Phosphor-Bronze  Company  by  Mr.  Stanger.  The  following1 


Engineering,  Aug.  9th,  1895,  p.  187. 


MODERN  STEAM  BOILER.  315 

are  the  results  obtained  with  a  special  alloy,  which  was  called 
by  the  Company  "  malleable  bronze." 


TABLE  LXIII. 


Material. 

Temper- 
ature 
Deg.  F. 

Breaking 
Stress. 
tons  per 
sq.  in. 

Elastic 
Limit, 
tons  per 
sq.  in. 

Extension 
per  cent, 
on  6  ins. 

Reduction 
of  area 
per  cent. 

Rolled  malleable  bronze 

cold 

3I'5I 

29-19 

8-2 

6ro 

Malleable  bronze  ... 

,, 

28-82               27-54 

9-0 

71-8 

,,               M 

400 

27-49               23-42 

8'3 

68-9 

1)                                M 

500 

26'H                24-70 

9-0 

67-0 

»            

6OO 

25-51                21-39 

10-8 

62-3 

A  large  number  of  experiments  with  other  metals  and  alloys 
are  summarised  in  Table  LXIV.  on  page  316. 

"  The  figures  given  for  gun-metal  show  a  critical  point  in  the 
temperature  strength  curve  at  about  350°  and  400°  F.,  since  there 
is  a  sudden  decrease  thjere  in  the  strength  and  elongation.  An 
increase  in  the  proportion  of  zinc  and  a  decrease  in  that  of  the 
tin  appear  to  raise  the  critical  point  somewhat,  as  shown  in  the 
figures  referring  to  the  brassy  gun-metal  in  next  columns.  In 
fact,  generally  speaking,  the  zinc-copper  alloys  are  much  less 
sensitive  to  temperature  changes  than  the  tin-copper  ones,  as  the 
results  for  yellow  metal  and  naval  brass  show.  The  addition  of 
i  per  cent,  of  aluminium  to  brass  is  stated  by  M.  Le  Chatelier  to 
improve  its  behaviour  in  this  respect  ;  common  castings  with 
this  addition,  totally  untreated  in  any  way,  show,  he  states,  a 
strength  of  12-5  tons  per  square  inch  when  tested  at  a  tem- 
perature of  480°  F.  He  therefore  recommends  the  use  of 
this  alloy  for  boiler  fittings  in  place  of  the  gun-metal  usually 
adopted." 


316 


THE  PRACTICAL  PHYSICS  OF 


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X 

w 

w 


R 
TI 


OPS 


^nr 


2       2S8888    8 

S       SS583S.  d 


S       SSoSSS    S       a    a 
2        o-ootf»     o.oo 


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•ni  01 
ojuou 


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s  .  .  .a  . 


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a     ss 


If  fithii  i  s  §  .§si 


THE  MODERN  STEAM  BOILER.  317 

The  following  diagram  (Fig.  141)  represents  graphically  the 
results  of  a  number  of  different  experiments  on  iron  and  steel, 
and  gives  them  in  a  convenient  form  for  comparison. 

It  was  taken  by  Professor  R.  H.Thurston1  from  German  sources, 
and  he  gives  the  following  explanatory  notes  : — 

"  Curves  Nos.  i  and  2  represent  Kollmann's  experiments  on 
iron  and  3  on  Bessemer  steel.  No.  i  is  ordinary  and  2  is  steely 
puddled  iron. 

"  Curve  No.  4  represents  the  work  of  the  Franklin  Institute  on 
wrought  iron. 


832      F. 


"  Curve  No.  5  gives  Fairbairn's  results,  working  on  English 
wrought  iron. 

"Nos.  6  to  ii  are  Styffe's,  and  represent  the  experiments 
made  by  him  on  Swedish  iron.  The  numbers  do  not  appear,  as 
these  results  do  not  fall  into  curves  ;  these  results  are  indicated 
by  circles,  each  group  being  identified  by  the  peculiar  filling  of 
the  circles,  as  one  set  by  a  line  crossing  the  centre,  another  by 
one  across,  a  third  by  a  full  circle,  etc. 

1  "  Manual  of  Steam  Boilers,"  etc.,  p.  83. 


3i8  THE  PRACTICAL  PHYSICS  OF 

"The  broken  lines  12  and  13  are  British  Admiralty  experiments 
on  blacksmith's  irons,  and  No.  14  on  Siemens'  steel.  The  first 
five  series  only  are  of  value  as  indicating  any  law  ;  and  they 
exhibit  the  general  tendency  to  a  decrease  of  tenacity  with 
increase  of  temperature. 

"  Fairbairn's  experiments,  No.  5,  best  exhibit  the  maximum, 
first  noted  by  the  Committee  of  the  Franklin  Institute,  at  a 
temperature  between  that  of  boiling  water  and  the  red  heat. 

"  It  will  be  observed  that  the  measure  of  tenacity,  at  the  left,  is 
obtained  by  making  the  maximum  of  Kollmann  unity.  It  will 
also  be  noted  that  Kollmann  does  not  find  a  maximum  as  in 
curves  4  and  5,  but,  on  the  contrary,  a  more  rapid  reduction  in 
strength  at  that  temperature  than  beyond.  It  would  seem,  there- 
fore, that  that  peculiar  phenomenon  must  be  due  to  some  accidental 
quality  of  the  iron.  The  author  has  attributed  it  to  the  existence 
in  the  iron,  before  test,  of  internal  stresses  which  were  relieved 
by  flow  as  the  metal  was  heated,  disappearing  at  a  temperature 
of  300°  or  400°  F.  (149°  to  294°  C.)." 

!  M.  CornuCs  Considerations. — With  reference,  however,  to  all 
the  results  which  have  been  obtained  with  iron  and  steel  when 
heated,  it  has  been  pointed  out  by  M.  Cornut,1  engineer-in-chief 
to  the  North  of  France  Association  of  Proprietors  of  Steam 
Boilers,  that  the  strains  have  been  referred  to  the  original  cross- 
section  of  the  specimen,  as  measured  before  being  tested,  and 
not  to  the  cross-section  at  the  moment  of  fracture  or  at  the  tem- 
perature to  which  the  specimen  had  been  raised.  As  it  appears 
that  the  loss  of  ductility  experienced  by  iron  and  steel  when 
heated  between  certain  temperatures  causes  the  section  of  frac- 
ture of  a  bar  to  be  larger  at  these  temperatures  than  at  the 
normal  temperature,  it  seems  to  be  necessary  to  ascertain  by 
measurement  what  are  the  dimensions  of  the  section  at  fracture, 
and  to  make  some  corrections  for  increase  of  size  and  increase 
of  brittleness  with  increased  temperature. 

One  of  the  most  recent  writings  on  the  subject  is  entitled 
4i  La  Temperature  et  les  Proprietes  Resistantes  des  Metaux,"  in 
the  Bulletin  de  la  Societe  d'encouragement  pour  1' Industrie 
Nationale,  for  August,  1899,  Tome  iv.,  Series  5,  No.  8,  pp.  1157— 
1200. 

1  Translated  by  B.  F.  Isherwood  in  Journal  of  the  Franklin  Inst.,  Vol.  cxix., 
pp.  257-266. 


THE  MODERN  STEAM  BOILER.  319 

Reference  should  also  be  made  to  an  exhaustive  series  of 
experiments  on  the  strength  and  ductility  of  bronze  in  relation 
to  temperature  which  is  described  by  C.  Bach  in  the  "  Zeitschrift 
des  Vereins  Deutscher  Ingenieure."  A  translation  into  English 
appeared  in  the  Engineer  of  5th  April,  1901,  p.  340. 

For  these  tests  25  cast  bronze  bars  were  supplied  by  the 
Imperial  Dockyard  at  Kiel,  the  tests  being  carried  out  as 
follows  : — 

A.  Four  bars  at  the  ordinary  temperature  of  64°  to  77°  Fahr. 

B.  Four     „     „    212°  Fahr. 

C.  Four     „     „    392°      „ 

D.  Five      „     „    572°      „ 

E.  Four     „     „  .  752°      „ 

F.  Four     „     „    932°      „ 

The  bronze  was  understood  to  have  the  composition  91  parts 
of  copper,  4  parts  of  zinc,  and  5  parts  of  tin,  but  analyses  made 
of  (a)  turnings  from  the  first  four  bars,  the  result  being  an 
average  ;  and  of  (b)  turnings,  afterwards  taken  from  bars  2  and 
4,  yielded  the  following  results  : — 

Turnings  from  all  Turnings  from 

4barsfa>  Bar  2.         (b)        Bar  4. 

Copper         per.  cent.     91*35  9r49  9r43  * 

Tin „  »  5H5  5'45               V50 

Zinc...  „  „  2*87  275  2-78 

Lead ,,  „  0*280  0*273  0-280 

Iron...         ...          ...  ,,  ,,  0*025  0-028  0*030 

Phosphorus...          ...  ,,  ,,  trace  trace  trace 

Arsenic         „  „           „  „                    „ 

Antimony „  „           „  „                    „ 

Sulphur,  etc.            ...  ,,  „           ,,  ,,                    ,, 

Summary  of  Tests. — The  bronze  tested  which  at  ordinary  tem- 
peratures had  a  breaking  stress  Kz  of  15-30  tons  per  sq.  inch,  an 
extension  0  of  36*27  per  cent.,  and  a  reduction  in  sectional 
area  ^  of  52*1  per  cent.,  had  the  following  values  at  the 
temperatures  noted  : — 

Temperatures  Fahr.          212°       392°       572°       752°       932° 
Kz  15-47     14-541     8.705     3-954     2-804 

</>  35'4       347       1 1 '5  °          ° 

^  47-4      48-2       16-2  o          o 


320  THE  PRACTICAL  PHYSICS  OF 

If  the  values  at  ordinary  temperatures  be  taken  in  each  case 
as  i,  then  the  following  proportional  figures  are  obtained  : — 

Breaking  stress  at 

68°  F.  212°  F.          392°  F.     572°  F.    752°  F.   932°  F. 

15-30  tons     15-457  tons     14-541       8-705       3-954       2*804 
=        i  roi  0-94          0-57         0-26         o'l8 

so  that  at  392°  F.  the  breaking  stress  is  reduced  by  6  per  cent., 
at  572°  by  43  per  cent.,  at  752°  by  74  per  cent.,  and  at  932  by 
82  per  cent. 

The  final  extension  at  212°  is  0-98  (unity  being  36-3),  at  392° 
it  is  0*96,  at  572°  it  is  0*32  or  68  per  cent,  reduction,  at  752° 
further  extension  can  no  longer  be  detected. 

Reduction  of  sectional  area  follows  a  similar  order  : — 

at  68°  F.     212°  F.     392°  F.     572°  F.     752°  F.     932°  F. 
52*1         47-4          48-2         16-2  o  o 

=       i  0*91  0*93         0*31  o  o 

It  follows  that  the  bronze  tested  might  be  used  for  valves 
pipes,  etc.,  with  steam  at  a  temperature  of  392°  F.,  but  not  in 
any  case  with  steam  at  572°  F.  If  that  limit  is  exceeded  the 
greatest  caution  should  be  observed. 

In  no  case  should  such  bronze  be  used  for  pipes,  etc.,  which 
are  to  carry  highly  superheated  steam,  and  even  with  moderately 
superheated  steam  its  use  is  not  advisable. 

Further  experiments  are  in  progress  as  to  the  results  writh 
bronze  of  different  composition. 

Although  572°  F.  is  the  temperature  estimated  for  saturated 
steam  of  1,000  Ibs.  per  sq.  inch  pressure,  yet  it  may  be  reached 
by  superheated  steam  of  a  much  less  pressure,  and  therefore  the 
use  of  such  bronze  may  be  attended  with  considerable  risk. 


CHAPTER  VII. 

CORROSION  AND  INCRUSTATION  IN  BOILERS. 

THE  preservation  of  boilers  from  chemical  actions  is  now 
fairly  well  understood  to  be  almost  entirely  a  question  of  clean- 
liness. Given  boiler  surfaces  of  a  good  quality  of  material,  kept 
free  from  deposits  of  foreign  metallic,  earthy,  or  oily  matters, 
and  supplied  with  fresh  water  from  which  the  suspended  or 
dissolved  gases  have  been  removed  and  are  excluded,  and  there 
is  no  fear  of  destructive  actions  proceeding. 

For  a  long  time  after  the  introduction  of  compound  marine 
engines  with  surface  condensers — say,  from  1856  onwards1  for 
many  years — engineers  had  to  face  a  difficulty  which  to  former 
practice  had  been  almost  a  total  stranger,  and  had  to  combat, 
whilst  they  at  the  same  time  investigated,  the  apparently  erratic 
and  mysterious  ravages  of  corrosion. 

Formerly  the  use  of  sea  water  in  marine  boilers,  like  that  of 
calcareous  waters  on  land,  resulted  in  a  greater  or  less  thiqkness 
of  incrustation  being  formed  on  the  interior  boiler  surfaces. 
Unless  this  was  allowed  to  form  to  a  considerable  extent  on  the 
parts  of  plates  or  tubes  exposed  to  the  direct  heat  of  the  tire  or 
furnace,  however,  there  was  no  danger  of  destructive  action  due 
to  the  presence  of  such  solid  deposits.  They  could  be  in  a  large 
measure  held  in  check  by  the  use  of  precipitants,  with  periodical 
blowing  off  the  mud  from  the  boilers,  on  land,  or  by  the  use  of 
brine  chests  or  regular  blowing  off  a  portion  of  the  contents  of 
the  boilers,  so  as  to  regulate  the  density  of  the  water  in  the 
boiler,  in  marine  practice.  No  doubt  this  practice  was  more  or 
less  barbarous,  and  involved  in  several  ways  the  loss  of  heat  ; 
but  as  long  as  deposits  of  lime  or  magnesia  coated  the  inner 
surfaces  of  boilers  they  were  safe  from  corrosive  action  from 
within.  We  can  now  see  that  in  the  days  when  tallow  was 
allowed  to  find  its  way  in  almost  unlimited  quantities  from  the 
engines  to  the  boilers,  such  a  protection  must  have  been  of  real 

1  See  Trans.  Inst.  E.  and  S.  in  Scot.,  Vol.  xxii.,  pp.  51-78;  Trans.  Inst. 
Naval  Arch.,  Vol.  xxx.,  pp.  108,  109. 

321  M 


322  THE  PRACTICAL  PHYSICS  OF 

service  to  them.  These  were  not  the  days  when  the  last  thermal 
unit  was  demanded  from  the  fuel,  and  the  highest  efficiency  in 
both  boiler  and  engine  was  striven  for,  and  consequently  engi- 
neers and  shipowners  did  not  object  to  waste  a  few  tons  of  coal, 
and  to  get  on  with  fewer  horse-power,  or  less  speed,  so  long  as 
boilers  could  be  readily  worked,  and  easily  protected  wrhen  out 
of  action.  At  the  same  time,  it  must  not  be  supposed  that 
engineers  -knew  they  were  wasting  fuel,  or  working  more  ineffi- 
ciently than  was  necessary,  but  only  that,  certain  arrangements 
having  been  arrived  at,  by  means  of  the  ordinary  process  of 
selection  of  the  readiest  method,  there  was  no  pressing  reason 
for  seeking  improvement  by  the  inevitable  path  of  pain  and 
trouble.  According  to  the  law  of  progress,  howrever,  that  was 
bound  to  come,  and  the  improvement  of  the  steam  engine  and 
spread  of  the  science  of  thermo-dynamics  introduced  the  inevit- 
able. 

When  the  question  of  boiler  corrosion  came  to  be  faced,  there 
had  been  but  little  real  advance  made  by  way  of  examining  the 
main  subject  of  corrosion  of  metals.  Locomotive  engineers 
had  experienced  some  trouble  from  corrosion  in  their  boilers, 
but  the  principal  investigations  carried  out  in  connection  with 
the  subject  had  been  made  either  as  scientific  experiments  or  in 
viewt)f  the  durability  of  iron  structures,  such  as  bridges  or  ships. 

Undoubtedly  there  were  several  workers  in  this  field,  and 
some  isolated  facts  concerning  the  corrosion  of  iron  had  been 
observed.  The  reports  made  by  Mr.  R.  Mallet,  M.R.I. A.,  to  the 
British  Association  (Reports  1838,  p.  253  ;  1840,  p.  221-308  ; 
and  1843,  P-  I~53)  giye  a  useful  summary  of  the  information 
available  at  the  time  when  his  experiments  were  undertaken. 
It  was  thus  made  known  that  dry  air  and  dry  oxygen  have  no 
action  on  iron  below  ignition  temperature,  that  pure  water 
deprived  of  air  also  has  no  action  below  212°  F.,  and  that  at 
common  temperatures  air  and  water  combined  act  energetically 
in  producing  rusting  or  oxidation.  Professor  Bonsdorf,  of  Hel- 
singfors,  had  added  the  information  that  air  perfectly  dry,  or  air 
saturated  with  water  vapour,  if  free  from  carbonic  acid,  has  no 
action  on  iron  ;  but  where  both  are  present,  and  also,  as  above, 
in  contact  with  both  air  and  water,  there  is  active  oxidation. 
The  action  of  sea  water  at  different  depths  and  different  tempe- 
ratures was  also  to  some  extent  studied  ;  but  these  researches 


THE  MODERN  STEAM  BOILER.  323 

remained  but  little  known  until  1872,  when  Mr.  Mallet  read  a 
paper  on  "  The  Corrosion  and  Fouling  of  Iron  Ships  "  to  the 
Institute  of  Naval  Architects  (vol.  xiii.,  pp.  90-162).  Even  then, 
however,  the  application  of  these  researches  to  steam  boilers  did 
not  at  once  appear,  and  did  not,  consequently,  suggest  itself  to 
engineers. 

Such  papers,  moreover,  as  those  "  On  Surface  Condensation  in 
Marine  Engines,"  by  Mr.  Edward  Humphrys,  of  Deptford,  and 
"  On  the  Effects  of  Surface  Condensers  on  Steam  Boilers,"  by 
Mr.  James  Jack,  of  Liverpool,  in  Proceedings  of  the  Institution 
of  Mechanical  Engineers,  1862,  page  99  ;  and  1863,  page  150, 
whilst  publishing,  or  eliciting  by  means  of  discussion,  the  main 
facts  as  to  the  corrosion  which  became  troublesome  in  boilers 
contemporaneously  with  the  use  of  surface  condensers,  served 
to  make  it  apparent  that  engineers  were  ignorant  both  of  its 
cause  and  of  a  remedy  for  it.  In  fact,  the  conclusion  emerging 
from  both  these  papers  and  discussions  is  that,  whilst  some 
corrosion  was  believed  to  be  due  to  fatty  acids  resulting  from 
decomposition  of  grease,  and  some  to  the  presence  of  particles 
of  brass  and  copper  in  the  boiler,  yet  the  real  cause  of  the 
corrosion  was  believed  to  be  the  "  distilled  water  itself,"  so  that, 
as  they  expressed  it,  "  by  constantly  boiling  the  same  water  over 
and  over  again  it  was  robbed  of  some  of  its  original  properties, 
or  became  otherwise  altered  in  quality  thereby,  so  as  to  produce 
the  serious  effects  that  were  experienced."  To  Faraday1  are 
due  the  suggestions  that  the  chloride  of  magnesium  in  sea  water 
is  capable  of  the  most  powerful  action  on  the  plates  of  boilers, 
and  that  voltaic  action  may  arise  in  a  boiler  through  the  contact 
of  copper  and  iron.  Others,  such  as  Mr."  F.  A.  Paget,  following 
R.  Mallet,  F.R.S.,  added  to  that  .the  idea  that  voltaic  action 
might  be  due  to  dissimilarity  in  composition  or  texture  between 
different  plates,  or  even  portions  of  the  same  plates,  in  a  boiler  ; 
and  one  observer  announced  that  the  steam  escaping  from  the 
safety  valve  of  a  boiler  using  sea- water  showed  a  distinctly  acid 
reaction,  some  of  the  corrosion  being  ascribed  to  this  as  a 
cause. 

The  first  direct  light  which  was  thrown  upon  the  subject  of 
corrosion  in  marine  boilers  was  obtained  from  some  careful 

1  Fifth  Report  of  the  Committee  of  the  House  of  Commons  concerning 
the  Holyhead  Roads,  p.  194. 

M2 


324  THE  PRACTICAL  PHYSICS  OF 

experiments  carried  out  by  the  late  Professor  Grace  Culvert,  of 
Manchester,  whose  researches,  though  published  about  1866, 
were  for  a  long  time  considered  of  interest  only  to  chemists  to 
whom  they  were  known.  Calvert  showed  incontestably  the 
effect  of  oxygen  and  carbonic  acid  (carbon-dioxide)  on  metals 
in  presence  of  moisture,  and  demonstrated  that  distilled  water 
free  from  air  or  gases  (and  even  that  dry  oxygen  or  dry  carbonic 
acid)  has  no  corrosive  action  on  pure  iron  or  steel.  Mr.  W. 
Kent,  a  distinguished  member  of  the  Stevens  Institute  of  Tech- 
nology, at  an  early  date  recognised  the  practical  value  of  these 
investigations,  and  by  means  of  them  was  able  to  explain  satis- 
factorily the  corrosion  of  iron  railway  bridges  in  the  United 
States  of  America.1  Their  application  to  the  case  of  boilers 
was  first  pointed  out  by  the  author  of  this  work  in  1876,*  \vho 
quoted  (see  Appendix  III.,  pp.  616,  617)  in  support  of  them  the 
results  of  later  researches  by  Professor  A.  Wagner,  which  also 
established  the  fact  that  the  presence  of  chlorides  of  magnesium 
sodium,  calcium,  and  other  chlorides  mentioned  by  him,  caused 
the  rusting  of  iron,  their  action  being  greatly  increased  by  the 
concurrent  presence  of  air  and  carbonic  acid  in  solution  in  the 
water,  except  in  the  case  of  magnesium  chloride,  which  attacked 
iron  in  the  absence  of  air. 

In  the  same  paper  (See  Appendix  1 1 1.,  pp.  618,619) tne  results  of 
a  careful  examination  of  the  effects  of  grease  in  condensed  water 
on  boilers  were  given,  so  that  the  range  of  that  action  should  be 
understood  ;  and  some  notice  will  be  found  in  it  of  the  subjects 
of  the  decomposition  of  the  chlorides  in  sea-water,  of  the 
presence  and  liberation  of  carbonic  acid  therein  under  the  action 
of  heat  and  pressure,  and  of  the  possibility  of  galvanic  action 
being  to  a  limited  extent  due  to  particles  of  copper  and  brass 
from  the  engines  carried  into  the  boilers. 

About  twelve  months  after  the  appearance  of  the  author's 
paper  "  On  Boiler  Incrustation  and  Corrosion,"  or  in  August, 
1877,  the  third  Report  of  the  Admiralty  "  Committee  appointed 
to  inquire  into  the  causes  of  the  deterioration  of  boilers,"  etc., 

1  See  the  Engineer  of  Aug.  13th,  1875. 

-  "  On  Boiler  Incrustation  and  Corrosion,"  by  F.  J.  Rowan,  read  before 
Section  G,  British  Association,  Glasgow,  1876,  and  recommended  for  publica- 
tion by  Section  G,  As  this  paper  is  put  of  print,  it  is  reproduced  in 
Appendix  III. 


THE  MODERN  STEAM  BOILER.  325 

was  issued  (the  previous  two  reports  having  been  of  a  preliminary 
character),  and  in  it  the  results  of  their  protracted  inquiry  were 
given,  as  well  as  the  conclusions  at  which  they  had  arrived  as  to 
the  causes  of  corrosive  action.  This  third  Report  emphasised 
the  same  facts  which  had  already  been  published  by  the  author, 
but  advanced  no  new  views  as  to  the  sources  of  corrosion.  Since 
the  latter  date  (August,  1877)  papers  on  this  subject  have  been 
written  by  Mr.  D.  Phillips,1  formerly  an  engineer  on  the  Admiralty 
Committee,  by  Mr.  J.  Farquharson,2  who  conducted  experiments 
for  the  second  Committee  (which  was  a  departmental  one) 
appointed  to  carry  on  the  investigation  after  the  first  Committee 
was  dissolved  ;  by  Mr.  W.  J.  Norris,3  Mr.  W.  Parker,4  Mr.  J.  B. 
Dodds,5  Prof.  V.  B.  Lewes,6  Mr.  J.  H.  Hallett,7  Mr.  C.  C. 
Lindsay,  Mr.  Sinclair  Couper,8  and  others,  and  reports  have  been 
issued  by  the  second  or  departmental  Committee  of  the  Admiralty. 
An  interesting  paper  on  u  Feed-water,  its  Effect  on  Steam  Boilers 
and  its  Treatment,"  read  by  Mr.  E.  G.  Constantine,  M.I.M.E.,  to 
the  Manchester  Association  of  Engineers,  in  April,  1890,  may  be 
consulted  ;  the  papers  by  Mr.  Thos.  Andrews,  F.R.S.E.,  on 
''  Galvanic  Action,  etc./'  in  Trans.  Roy.  Soc.  Edin.,  and  in  Min. 
Proc.  Inst.  C.E.,  should  be  carefully  considered  ;  and  also  an  im- 
portant paper  by  Mr.  Thos.  Turner,  A.R.S.M.,  F.I.C.,  Lecturer  on 
Metallurgy  at  Mason's  College,  Birmingham,  on  "  The  Corrosion 
of  Iron  and  Steel,"  read  to  the  South  Staffordshire  Inst.  of  Iron 
and  Steel  Works  Managers  in  February,  1894. 

Relative  Corrosion  of  Iron  and  Steel. — The  investigations  and 
papers  by  Mr.  Phillips,  Mr.  Farquharson,  and  Mr.  Parker,  were 
occupied  principally  with  the  question  of  the  comparative  rates 
of  wasting  or  corrosion  in  iron  and  mild  steel,  and  it  appeared 
that,  in  general,  mild  steel,  perhaps  on  account  of  its  purity,  is 

1  Min.  Proc.  Inst.  C.  E.,  Vols.  Ixv.,  pp.  73-97  and  98-138,  and  Vol.  Ixxxv. 
P-  295- 

'  Trans.  Inst.  N.  A.,  Vol.  xxiii.  (1882),  pp.  143-150. 

3  Trans.  Jnst.  N.  A.,  Vol.  xxiii.,  pp.  151-162. 

4  Jour.  Iron  and  Steel  Inst.,  1879,  p.  53  and  1881,  p.  49. 

5  Trans.  N.E.  Coast  Inst.  Eng.  and  S.,  Vol.  v.,  p.  195. 

6  Trans.    Inst.    N.  A.,  Vol.  xxviii.,  p.  247,  Vol.  xxx.,  pp.  330-362,  and  Vol. 
xxxii.,  p.  67. 

7  Proc.  Inst.  Mech.  Eng.,  1884,  p.  331. 

"  Trans.  Inst.  E.  and  S.  in  Scotland,  Vol.  xl.,  pp.  41-106,  Vol.  xxiv., 
pp.  77-118. 


326  THE  PRACTICAL  PHYSICS  OF 

more  liable  to  rapid  oxidation  than  wrought  iron,  as  wrought 
iron  in  this  matter  precedes  cast  iron.  When,  however,  both 
wrought  iron  and  steel  plates  were  used  in  the  same  structure,  or 
where  steel  plates  were  fastened  with  wrought-iron  rivets,  the 
results  were  conflicting  ;  in  some  cases  the  steel,  and  in  others 
the  iron,  showed  the  greater  amount  of  corrosion. 

As  the  main  question  here  is  not  steel  versus  iron,  but  is  the 
action  of  corrosion  and  how  to  prevent  it,  we  must  practically 
pass  over  these  papers  and  many  experiments  made  by  or  at  the 
instance  of  both  Committees  on  boilers.  The  main  facts  as  to 
the  relative  corrosion  of  iron  and  steel  have  been  well  sum- 
marised by  Mr.  Turner  in  the  paper  referred  to.  The  following 
is  an  extract  from  it  : — 

"  The  differences  of  opinion  on  this  subject  have  arisen,  the 
author  believes,  on  account  of  conclusions  being  drawn  from 
limited  observation,  or  special  circumstances  ;  while  much  con- 
fusion has  arisen  from  failing  to  recognise  that  the  conditions  in 
fresh  water,  salt  wrater,  the  interior  of  a  boiler,  or  in  diluted 
acids,  are  all  different,  and  that  a  specimen  which  may  very 
successfully  resist  corrosion  in  one  of  these  cases  may  readily 
^xidize  in  another.  On  account  of  the  greater  uniformity  in  the 
physical  properties  of  steel,  and  the  laminated  character  of  iron, 
it  was  anticipated  in  the  early  days  of  the  use  of  mild  steel  that 
it  would  resist  corrosion  much  better  than  wrought  iron.  Thus 
Sir  L.  Bell1  expressed  the  opinion  that  the  cinder  in  wrought- 
iron  rails  would  set  up  galvanic  currents,  and  thus  lead  to  more 
rapid  corrosion.  Experience  has  however  shown  that  on  lines 
where  there  is  very  little  traffic,  and  the  chief  agent  of 
destruction  is  corrosion,  wrought-iron  rails  wear  better  than 
steel. 

"The  result  of  the  experiments  of  the  Admiralty  Committees 
which  were  appointed  to  consider  the  causes  of  the  deterioration 
of  boilers,  and  which  issued  Reports  in  1877  and  1880,  led  to 
the  conclusion  that  in  all  cases  wrought  iron  resisted  corrosion 
better  than  steel.  Where  the  conditions  were  not  severe  the 
differences  observed  were  not  great  ;  but  where  the  plates  were 
daily  dipped  in  water,  and  exposed  during  the  rest  of  the  time 
to  the  action  of  the  atmosphere,  the  superiority  of  iron  was  very 

1  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1878,  p.  97. 


THE  MODERN  STEAM  BOILER.  327 

marked  ;  while  common  iron  was  less  affected  by  corrosion 
than  best  Yorkshire  iron,  which  is  in  accordance  with  the 
statement  of  Gmelin  that  phosphorus  diminishes  corrosion  in 
iron.  The  following  percentages  in  favour  of  iron  were  obtained 
in  these  experiments  : — 

Common  iron  resisted  corrosion  better 

than  Yorkshire  iron  ...  ...  ...  9*6  per  cent. 

Yorkshire  iron  resisted  corrosion  better 

than  mild  steel  ...  i6'o  „ 

"  In  another  series  of  experiments,  conducted  by  Mr.  D. 
Phillips,  in  Cardigan  Bay,  and  lasting  for  seven  years,  it  was 
found  that  the  average  corrosion  of  mild  steel  during  the  whole 
period  was  126  per  cent,  more  than  wrought  iron.1  Indepen- 
dent experiments  conducted  by  Mr.  T.  Andrews2  also  showed 
that  wrought  iron  corroded  less  rapidly  than  mild  steel,  when 
the  cleaned  metallic  surfaces  were  exposed  to  the  action  of  sea- 
water.  The  conclusions  of  the  Admiralty  Committee  and  of 
Mr.  Phillips  aroused  much  adverse  criticism,  and  it  was  shown 
that  though  steel  is  more  affected  by  ordinary  atmospheric 
corrosion,  it  is  not  usually  more  affected  when  in  the  form  of  a 
steel  boiler.  This  was  stated  by  Mr.  W.  Parker,3  who  based 
his  conclusions  on  the  result  of  over  1,100  actual  examinations 
of  boilers  ;  and  his  observations  wrere  confirmed  by  experienced 
makers  and  users  of  boilers,  who  took  part  in  the  discussion  of 
his  paper." 

Sir  W.  Siemens  also  stated  that  experiments  at  Landore  had 
shown  similar  results,  and  Sir  H.  Bessemer4  bore  testimony  to  the 
same  effect,  while  "  Mr.  W.  John,5  as  the  result  of  considerable 
experience  in  the  construction  of  ships,  stated  that  the  protection 
of  mild  steel  ships  from  corrosion  was  purely  a  question  of  care 
and  maintenance,  and  the  correctness  of  this  view  has  been  fully 
proved  in  the  interval  that  has  since  elapsed. 

"  It  is  generally  believed  that  the  presence  of  manganese  in  steel 
increases  the  readiness  with  which  it  rusts  or  corrodes. 


1  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixv.,  p.  73  ;  Proc.  Inst.  Mar.  Eng.,  May,  1890. 

2  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixxvii.,  p.  323,  Vol.  Ixxxii.,  p.  281. 

3  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1881,  p.  39. 

4  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixv.,  p.  101. 

5  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1884,  p.  151. 


328  THE  PRACTICAL  PHYSICS  OF 

(<  This  view  was  held  by  Sir  \V.  Siemens,1  who  stated  that  as 
manganese  in  mild  steel  increased,  so  the  tendency  to  corrode 
became  greater  ;  while  Mr.  G.  J.  Snelus2  has  ascribed  the  'pitting' 
in  steel  to  the  irregular  distribution  of  manganese  in  the  metal." 

The  experiments  of  Faraday  led  him  to  the  conclusion  that 
most  of  the  alloys  of  steel  with  other  metals  corrode  less  readily 
in  moist  air  than  unalloyed  steel  ;  but,  according  to  Mallet,3  the 
alloys  of  potassium,  sodium,  barium,  aluminium,  manganese, 
silver,  platinum,  antimony  and  arsenic  with  iron,  corrode  more 
rapidly  than  pure  iron  ;  while  the  presence  of  nickel,  cobalt,  tin, 
copper,  mercury  and  chromium  affords  protection,  the  effect 
being  in  each  case  in  the  order  given. 

Later  French  writings  confirm  this  as  regards  the  presence  of 
nickel. 

Evidence  of  Bias  in  Papers. — Regarding  the  later  writings  on 
boiler  corrosion,  a  curious  phenomenon  is  often  seen  in  the 
publications  or  papers  dealing  with  this  subject.  An  author 
desires  to  show  that  corrosion  in  boilers  always  proceeds  from 
one  particular  cause,  which  he  is  satisfied  is  the  true  one.  He 
thereupon  gives  details  or  descriptions  of  other  causes  which 
have  been  suggested  by  others,  and  is  careful  to  call  them 
"  theories,"  in  an  objectionable  wray,  i.e.,  with  the  view  of  dis- 
crediting them  out  of  hand  or  of  prejudicing  opinion  about  them. 
He  then  selects  examples  of  corrosion  which  do  not  fit,  and 
doubtless,  were  never  supposed  to  fit,  any  of  these  so-callecl 
"  theoretical  "  causes,  but  which  do  fit  in  with  the  one  which  he 
has  selected  for  approval,  and  thus  he  conclusively  proves  his 
point  and  triumphantly  dismisses  the  defamed  "  theories."  A 
little  consideration  would,  however,  show  that  it  is  never  sup- 
posed by  any  \vho  have  studied  the  subject  that  there  is  one 
universal  cause  for  all  instances  of  corrosion,  or  that  any  special 
cause  dominates  every  case  unless  an  exceptional  one.  There 
are  several  causes  or  agencies  usually  at  work,  and  not  all  are  to 
be  found  operative  in  any  one  case,  nor  are  the  same  ones 
operative  in  each  case.  Usually  certain  causes  are  more  promi- 
nently found  in  one  case,  and  different  ones  in  another  ;  the 
conditions  under  which  the  individual  boiler  is  worked  having 

1  Jour.  Iron  and  Steel  Inst,  Vol.  i.,  1878,  p.  44. 

2  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1881,  p.  66. 

3  B.  A.  Reports,  1838,  p.  266. 


THE  MODERN  STEAM  BOILER.  329 

naturally  a  great  influence  on  the  special  kind  of  action  to  which 
it  becomes  subject. 

Another  thing  becomes  evident  on  a  survey  of  the  literature  of 
corrosion,  and  that  is  that  the  answer  to  the  objections  or 
difficulties  of  one  author  or  investigator  is  usually  to  be  found  at 
hand  in  the  work  of  another,  not  seldom  having  been  published 
before  the  appearance  of  the  objection. 

Galvanic  Action. — It  is  remarkable  that  in  the  records  of  all 
the  earlier  researches  into  corrosive  action,  the  greatest  stress 
was  laid  upon  voltaic  action,  or  what  was  termed  the  action  of 
galvanic  currents,  as  being  the  prime  cause  of  corrosion.  This 
was  usually  expressed  in  such  a  way  as  to  convey  the  idea  that 
the  mere  presence  of  dissimilar  metals,  or  qualities  of  metal,  in 
contact,  is  enough  to  start  corrosive  action,  and  that,  as  even  a 
modern  chemist  has  expressed  it,  "  there  must  be  great  chemical 
action  due  to  the  formation  of  a  galvanic  current."  While, however, 
it  is  true  that  the  passage  of  an  electric  current  through  a  liquid 
between  metals  or  bodies  of  opposite  relations,  considered  elec- 
trically, causes  chemical  action  to  take  place  by  which  one 
element  becomes  corroded  or  eaten  away  ;  yet  the  analogy  of  a 
galvanic  cell  shows  that  it  is  the  chemical  action  which  causes 
the  appearance  of  an  electric  current,  so  that  to  say  "  the 
chemical  action  due  to  the  formation  of  a  galvanic  current," 
seems  to  reverse  the  proper  order.  No  one  can  say  that  the 
statement  is  wrong,  nevertheless,  because,  for  all  that  we  know, 
the  electric  may  be  the  initiatory  and  directive  form  of  the 
energy  which  first  becomes  sensible  to  us  as  chemical  action. 
Where  there  is  such  chemical  action  proceeding  as  the  union  of 
a  metal  (such  as  iron)  with  oxygen,  resulting  in  the  formation  of 
oxide,  there  is  certain  to  be  the  evidence  of  more  or  less  heat 
and  electricity.  When  under  such  circumstances  electrically 
dissimilar  metals  or  substances  are  present  in  contact,  the  effect 
of  that  arrangement  is  to  determine  the  direction  of  flow  of  the 
electrical  energy,  which  becomes  apparent  as  current,  so  that  the 
electro-positive  element  becomes  the  one  which  suffers  most  from 
the  chemical  action.  It  has,  however,  been  proved  that  in  some 
cases — and  the  oxidation  or  rusting  of  iron  is  one  of  them — the 
accumulation  of  oxygen  at  the  positive  pole  has  the  effect  of  in 
time  polarising  the  galvanic  couple  and  the  action  is  hindered  if 
not  reversed.  In  some  instances  of  corrosion  a  reversal  of  the 


33°  THE  PRACTICAL  PHYSICS  OF 

direction  of  the  electrical  current  has  been  noticed.  It  was 
pointed  out  by  Mr.  D.  Phillips  l  that  while  in  some  cases  much 
local  action  had  been  observed  when  iron  rivets  had  been  used 
in  steel  boilers,  there  were  numerous  cases  of  such  construction 
where  no  injurious  effects  had  been  noticed.  Some  experiments 
communicated  to  the  Institution  of  Marine  Engineers  by  Mr.  J. 
Farquharson 2  sho\ved  that  while  some  steel  plates  which  were 
tested  alone  "  lost  about  12  ounces  by  corrosion  and  iron  plates 
when  similarly  tested  lost  about  1 1  ounces,  if  the  two  dissimilar 
plates  were  in  electric  contact,  the  steel  lost  only  about  4  ounces, 
while  the  iron  lost  21  ounces,"  showing  that  in  this  case,  at  all 
events,  the  iron,  from  whatever  cause,  acted  as  electro-positive 
to  the  steel.  Mr.  W.  Denny3  also  recorded  the  case  of  a  steel 
ship  in  which  the  corrosion  shown  wras  "  not  in  the  steel,  but  in 
the  iron  stern-frame  and  rudder  forgings  and  in  some  small  iron 
plates  on  the  rudder,  the  large  steel  plates  of  the  rudder  and  the 
whole  shell  plating  of  the  ship,  which  was  of  steel,  being 
perfectly  free  from  corrosion."  On  the  other  hand  Mr.  B. 
Martell4  instanced  the  case  of  a  steel  ship  which  he  had 
examined  in  the  North  of  England  (when  hauled  up  on  a  slip- 
wray  after  less  than  a  year's  employment  at  sea)  as  having  shown 
rapid  deterioration  of  the  steel  plates  where  they  had  been 
exposed  alternately  to  sea- water  and  to  air.  "The  vessel  was 
riveted  wTith  iron  rivets,  and  he  found  that  between  the  light- 
water  mark  and  the  load-water  mark,  which  was  alternately  wet 
with  sea-water  and  then  dry  and  exposed  to  the  air,  a  rapid 
deterioration  had  taken  place  as  compared  with  the  other  parts 
of  the  vessel,  and  with  iron  vessels  ;  in  fact,  the  steel  round  the 
rivets  had  w7asted  to  a  considerable  extent,  so  that  the  rivet 
points  \vere  protruding  some  distance  beyond  the  steel.  He 
thought  it  might  probably  be  due  to  galvanic  action."  It  is 
evident  that,  as  Mr.  Turner  has  suggested,  the  explanation  of 
the  apparently  contradictory  results  noticed  by  previous  observers 
is  probably  to  be  found  in  the  observations  by  Mr.  T.  Andrews 5 

1  Proc.  Inst.  Marine  Eng.,  May,  1890. 

2  Proc.  Inst.  Marine  Eng.,  March,  1882. 

3  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1881,  p.  63. 

4  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixv.,  p.  103. 

5  Min.  Proc.  Inst.  C.  E.,  Vol.  Ixxvii.,  pp.  323-334.     See  also  Trans.  Roy.  Soc. 
Edin.,  Vol.  xxxii.,  pp.  204-218. 


THE  MODERN  STEAM  BOILER.  331 

in  the  course  of  some  experiments  on  the  galvanic  action 
between  different  varieties  of  iron  and  steel  during  exposure  to 
sea- water.  "In  these  experiments  metal  of  known  chemical 
composition  was  employed  in  the  form  of  round  rods  which 
were  carefully  turned  and  polished  before  use.  The  rods  were 
immersed  in  sea-water  in  a  standard  cell,  together  with  a 
standard  rod  of  wrought  iron,  and  frequent  observations  of  the 
electro-motive  force  of  the  couple  were  made  with  a  delicate 
galvanometer.  Though  it  was  observed  that  the  standard 
wrought-iron  was  electro-negative  to  all  the  samples  tested,  it 
was  also  noticed  during  a  lengthy  course  of  experiments,  that  a 
complete  interchange  of  electro-chemical  position  occurred  in 
the  case  of  every  metal  at  various  times  during  the  observations. 
These  interchanges  of  position  sometimes  took  place  even  after 
considerable  intervals,  and  it  is  doubtful  whether  a  permanent 
position  of  rest  finally  ensues  between 'the  two  metals,  though 
eventually  the  galvanic  action  becomes  very  small."  These 
results  were  afterwards  corroborated  by  some  gravimetrical 
experiments  carried  out  by  Mr.  Andrews  and  communicated  to 
the  Inst.  C.  E.1  There  is  little  doubt  that  they  supply  the 
explanation  sought  for. 

Mr.  Andrew's  also  communicated  the  results  of  a  series  of 
experiments  to  the  Royal  Society  of  Edinburgh  2  which  showed 
that  "  wrought-iron  and  steels  are  not  static  in  their  electro- 
chemical positions,  and  when  immersed  in  sea-water,  or  other 
solutions,  in  connection  with  each  other,  cannot  exactly  be 
regarded  as  constant  elements.  The  relative  electro-chemical 
position  is  also  varied  according  to  the  nature  of  the  solutions 
employed." 

Full  details  of  the  chemical  constitution  and  physical  properties 
of  the  various  specimens  of  steel,  wrought  and  cast-iron  used  in 
the  tests,  are  given  in  a  series  of  Tables  in  Mr.  Andrews'  paper, 
which  must  be  consulted  for  these  details.  Tables  of  the 
galvanic  tests,  and  curves  graphically  representing  the  results, 
are  also  given,  and  these  show  that  although  the  galvanic  action 
is  usually  vigorous  on  starting  with  bright  and  clean  surfaces,  yet 
the  accumulation  of  oxide  soon  diminishes  its  activity  and 
frequently  reversals  of  polarity  become  evident. 

1  Min.   Proc.  Inst.  C.  E.,  Vol.  Ixxxii.,  p.  281.     See  also  Vol.  cxviii.,  p.  356. 

2  Transactions,  Vol.  xxxii.,  pp. 204-218. 


332  THE  PRACTICAL  PHYSICS  OF 

In  general,  in  sea-water,  all  the  steels  as  well  as  the  wrought 
iron  and  cast  iron  appeared  on  first  being  immersed  to  be 
negative  to  zinc  rods,  when  these  formed  the  other  member  of 
the  couples. 

Soft  Siemens- Martin  steel,  cast  iron  and  Tungsten  steel  appeared 
to  be  positive  to  the  wrought- iron  standard  bar  employed  by  Mr. 
Andrews,  whilst  both  hard  and  soft  Firth's  steel,  Bessemer  steel, 
puddled  steel  and  puddled  steel  chilled  were  electro-negative  to 
the  wrought  iron. 

All  these  metals  without  distinction  appeared  on  immersion  in 
sea-water  to  be  positive  to  bars  of  iron  coated  with  the  oxide 
from  the  rolling  mills. 

In  acid  colliery  water  all  the  metals  were  negative  to  zinc  ; 
all  were  negative  to  the  wrought-iron  bars,  except  Tungsten  steel, 
which  was  first  positive  and  afterwards  negative.  All  were 
positive  to  bars  coated  with  iron  scale. 

In  sea- water  also  all  the  metals  in  the  form  of  plates  with 
bright  surfaces  were  positive  to  bright  copper  plates. 

A  series  of  plates  were  prepared  bent  in  the  form  of  an 
inverted  U  (thus  f|)>  having  one  limb  polished  bright,  and  the 
other  coated  with  mill  scale,  and  these  were  immersed  in  sea- 
water  in  porous  cells  and  coupled  together  in  series  electrically. 
The  bright  side  was  invariably  positive  to  that  coated  with  oxide, 
and  the  action  was  at  first  energetic  between  them,  but  in  the 
course  of  about  four  days  the  current  diminished  and  died 
away  to  almost  nothing. 

•"It  may  therefore  be  concluded,"  writes  Mr.  Turner,  "  that 
though  with  dissimilar  metals,  such  as  cast  iron  and  wrought 
iron,  the  galvanic  action  may  be  considerable,  in  the  case  of 
materials  which  are  more  alike,  such  as  wrought  iron  and  mild 
steel,  it  is  exceptional  for  the  corrosion  from  galvanic  action  to 
be  very  great,  although  its  occurrence  should  never  be  over- 
looked ;  and  when  this  action  does  occur,  though  it  usually  leads 
to  the  corrosion  of  the  steel,  yet  it  not  infrequently  has  a 
contrary  influence.  The  danger  of  greatly  increased  corrosion 
with  dissimilar  metals  is  much  diminished  by  their  tendency  to 
polarize  each  other's  action,  and  thus  lead  to  an  inter- 
change of  electro-chemical  position.  Galvanic  action  between 
wrought  iron  and  steels  also  appears  to  be  materially  reduced 
in  course  of  time,  otherwise  the  liability  to  destructive 


THE  MODERN  STEAM  BOILER.  333 

corrosion,    though    never    incorrsidei able,   would    be    more    for- 
midable." 

Influence  of  Stress  on  Corrosion. — We  are  indebted  to  Mr. 
Andrews '  for  the  further  research  which  has  demonstrated  the 
effect  of  stress  on  corrosive  action.  It  was  known  that  stress, 
whether  tensile,  rlexional,torsional,  or  of  any  other  kind,  consider- 
ably alters  the  physical  properties  of  iron  and  steel  ;  increases 
the  rigidity  of  both  iron  and  steel,  and  renders  the  metal  harder, 
also  greatly  reducing  its  properties  of  elongation  or  ductility. 
"  A  higher  tonnage  is  required  to  break  a  '  strained  '  than  an 
'  unstrained  '  portion  of  the  same  metal.  A  tensile  stress  applied 
to  a  wrought- iron  shaft,  producing  an  elongation  of  only  2  per 
cent,  increased  the  tensile  resistance  of  the  metal  2'66  per  cent." 
"  It  is  manifest,"  Mr.  Andrews  remarked,  "  that  the  stresses, 
applied  to  the  metals  examined  for  corrosion,  altered  their 
structure,  rendered  them  harder  in  nature,  and  hence  less  liable 
in  the  strained  condition  to  be  acted  upon  by  sea-water,  or  other 
waters,  than  in  their  ordinary  or  softer  condition.  The  experi- 
ments, however,  indicated  that  an  increased  total  corrosion,  in 
excess  of  the  normal  corrosibility  of  the  metal,  occurs  in  a 
metallic  bridge,  vessel,  boiler,  or  other  structure  from  the  action 
of  the  local  galvanic  currents  which  wrere  shown  to  be  induced 
between  '  strained '  and  *  unstrained '  portions  of  even  the 
same  piece  of  iron  or  steel  forging,  bar,  or  plate.  Hence  a 
strain  occurring  in  a  metallic  structure  tends,  owing  to  the  local 
galvanic  action  thus  set  up,  to  increase  any  corrosive  forces 
which  may  be  deteriorating  the  metal  of  which  it  is  composed." 
The  explanation  of  the  corrosion  of  ship's  plates  between 
punched  rivet  holes  may  be  found  in  this,  and  reflectively 
it  supplies  an  argument  against  punching.  Such  researches 
throw  needed  light  upon  the  causes  which  determine  the  course 
and  the  rapidity  of  corrosive  action,  but  it  must  be  remembered 
that  were  all  other  elements  of  chemical  action  absent,  the  mere 
presence  of  dissimilar  electro-chemical  or  physical  qualities  in 
metals  in  contact  could  not  of  itself  create  corrosive  action. 
That  is  to  say,  that  if  dissimilar  metals  or  qualities  of  metal  were 
in  metallic  contact,  and  immersed  in  a  liquid  which  has  no 

1  Min.  Proc.  Inst.  C.  E.,  Vol.  cxviii.,  p.  356.  See  also  Proc.  Royal  Soc.,  Vols. 
xlii.,  459  ;  xliv.,  152  ;  xlvi.,  176  ;  lii.,  114  ;  Proc.  Fed.  Inst.  Mining  Engineers, 
Vol.  i.,  191  ;  Min.  Proc.  Inst.  C.E.,  Vols.  Ixxxvii.,  340  ;  xciv.,  180  ;  cv.,  161. 


334  THE  PRACTICAL  PHYSICS  OF 

chemical  action,  or  contains  no  gases  which  have  chemical 
action,  on  the  metal,  there  would  not  be  any  evidence  of 
galvanic  current.  But,  conversely,  where  chemical  action  is 
present,  combined  with  electro-chemical  dissimilarity,  there  must 
be  galvanic  action,  in  spite  of  such  reasoning  as  that  of  Mr.  W. 
J.  Morris1  to  the  contrary.  The  distinguishing  characteristics 
of  chemical  action  that  is  entirely  local  and  of  that  which  is,  or 
may  become  voltaic,  are,  of  course,  not  entered  into  here. 

Influence  of  Mill  Scale  or  Oxide. — The  presence  of  mill  scale, 
or  that  quality  of  black  oxide  which  is  produced  in  rolling  mill 
or  forge  furnaces,  on  the  surface  of  iron  or  steel,  has  been  found 
to  be  an  active  cause  of  the  production  of  galvanic  currrents  in  a 
sense  adverse  to  the  metal  plates  to  which  the  scale  adheres. 

Electrical  Activity  of  Oxides. — Mr.  Andrews' experiments  demon- 
strate the  reason,  and  the  fact  that  damage  is  caused  wrhen  such 
scale  is  present  is  abundantly  testified  to  by  Mr.  W.  Parker,2 
Sir  N.  Barnaby,3  Sir  W.  H.  White,4  Mr.  J.  Farquharson,5  and 
Professor  V.  B.  Lewes.6  The  latter  made  some  interesting  tests, 
comparing  the  electrical  activity  of  the  oxides  with  that  of  the 
metal.  "  Some  steel  plates,  4  inches  by  i  inch,  were  cut  from 
the  same  sheet  and  were  faced  on  one  side.  On  the  polished 
surface  of  one  a  piece  of  thin  blotting-paper  was  laid,  so  as  to 
entirely  cover  it,  and  project  half  an  inch  beyond  its  edges. 
This  was  wetted  with  sea-water,  and  the  other  plate,  writh  its 
polished  face  downwards,  was  placed  on  the  wet  paper,  so  that 
the  two  polished  steel  faces  were  separated  by  the  blotting- 
paper  soaked  with  sea- water.  Wires  were  then  placed  in  contact 
with  the  dry  backs  of  the  plates,  and  fixed  in  position  by  a  dry 
wooden  clamp.  On  connecting  this  couple  with  a  Thomson's 
marine  reflecting  galvanometer,  a  deflection  of  20°  on  the  scale 
was  obtained.  The  upper  plate  was  then  raised,  and  smeared 
over  with  a  thin  paste  of  magnetic  oxide  mixed  \vith  sea-\vater. 
It  was  then  replaced  in  position,  giving  a  deflection  of  112°  on 

1  See  Trans.  Inst.N.  A.,  Vol.  xxiii.  (1882),  pp.  151-161  ;  also  Engineering,  28th 
July,  1882,  page  96. 

2  Jour.  Iron  and  Steel  Inst,  Vol.  i.,  1881,  pp.  48-53. 

3  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1879,  p.  53. 

4  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1881,  p.  68. 

5  Min.  Proc.  Inst.,  C.  E.,  Vol.  Ixv.,  p.  105. 

6  Trans.  Inst.  N.  A.,  Vol.  xxviii.,  1887,  p.  247;   Jour.  Iron  and  Steel  Inst., 
Vol.  i.,  1887,  p.  461. 


THE  MODERN  STEAM  BOILER.  335 

the  scale.  The  plates  were  then  carefully  cleaned  and  dried; 
fresh  blotting-paper,  moistened  with  sea-water,  was  placed 
in  position,  and  the  upper  plate  was  smeared  with  hydrated 
ferric  oxide  and  sea-water  and  placed  upon  it.  This  gave 
a  deflection  of  65°  ;  whilst  hydrated  ferrous  oxide  only 
gave  a  deflection  of  25°,  or  very  little  more  than  the  plates  by 
themselves  ;  portions  of  a  rust  cone  treated  in  the  same  way  gave 
a  deflection  of  110°.  In  each  case  the  reading  was  taken  imme 
diately  the  needle  came  to  rest,  and  in  all  cases  the  curren 
rapidly  diminished,  but  generally  recovered  again  on  standing 
in  circuit.  A  small  cell  made  of  crushed  rust-cones  from  H.M.S 
'  Inflexible/  after  standing  on  short  circuit  for  a  week,  gave  a 
constant  deflection  of  108°.  These  deflections  were  all  much 
increased  on  using  sea-water  through  which  carbonic  acid  and 
air  had  been  passed."  This  latter  only  showed  that  the  water 
wras  thus  made  a  more  active  corroding  agent,  because  as  the 
chemical  action  increases  in  intensity  so  the  display  of  electrical 
energy  is  more  pronounced.  From  these  data  Professor  Lewes 
concluded  that  it  is  easy  to  explain  the  formation  of  rust  cones, 
and  the  consequent  or  concurrent  pitting  of  the  plates  of  ships. 
a  On  the  metal  of  the  ship  there  is  a  small  particle  of  moist  rust 
left  when  the  ship  was  last  scraped,  or  else  formed  by  a  particle 
of  some  foreign  metal,  or  the  perishing  of  the  protective.  The 
moist  rust  forms  a  galvanic  couple  with  the  iron,  and  slowly 
decomposes  the  moisture  ;  the  oxygen  oxidising  the  iron.  The 
hydrogen,  on  the  other  hand,  gently  pushes  up  the  protective 
and  anti-fouling  coats,  forming  a  small  blister.  The  sea-water 
leaks  in,  an  active  galvanic  current  is  produced,  and  the  blister 
slowly  nils  with  the  rust  resulting  from  that  action.  The  con- 
tinuation of  the  action  gives  the  larger  rust  cones.  This  process 
being  independent  of  the  oxygen  dissolved  in  the  sea-water,  and 
the  amount  of  water  present  being  small,  the  corrosion  gives  rise 
to  the  ferrous  as  well  as  the  ferric  oxide." 

On  this  subject  Mr.  W.  John l  recorded  "  the  case  of  a  steel 
ship  which  had  been  launched  just  six  weeks  and  then  docked, 
to  receive  her  engines  and  boilers  ;  and  although  she  had  been 
carefully  painted  before  launching,  with  a  good  composition 
specially  chosen  by  the  owners,  many  of  the  plates  presented  a 

1  Jour.  Iron  and  Steel,  Inst.,  Vol  i.,  1884,  pp.  138-181. 


336  THE  PRACTICAL  PHYSICS  OF 

most  curious  appearance  of  pitting.  They  were  scattered  about 
in  some  parts  without  any  apparent  connection,  and  in  others, 
the  little  mole-hills  of  rust  seemed  to  have  an  order  of  their  own, 
either  in  curves  or  straight  lines.  He  was  so  much  struck  with 
the  case  that  he  examined  it  very  thoroughly,  and  as  the  rust 
dried  in  the  little  mounds  he  carefully  scraped  a  number  of 
these  off  with  a  knife,  without  injuring  the  paint."  It  then 
appeared  that  although  the  rust  was  formed  into  little  hemis- 
pheres of  about  | in.  diameter  outside  the  paint,  the  hole  in  the 
paint  was  not  more  than  the  size  of  a  pin  head,  and  that  in  each 
case  it  was  easy  to  pick  out  a  loose  particle  of  black  oxide  em- 
bedded in  a  little  pit  in  the  plate,  so  that  the  active  cause  of  the 
local  action  was  very  apparent.  Although  these  results  have 
been  observed  in  the  case  of  iron  or  steel  ships  immersed  in  sea- 
water,  yet  they  are  no  doubt  analogous  to  those  often  noticed  in 
the  case  of  boiler  plates  or  tubes.  And  even  where  the  elements 
of  galvanic  action  may  not  be  present  in  any  marked  degree,  yet 
the  chemical  processes  involved  in  the  corrosion  or  pitting 
require  very  fewr  conditions  for  their  being  present  in  activity. 

Summary  of  Chemical  Processes  Involved. — These  conditions 
have  been  referred  to  already,  but  may  be  reviewed  in  the  form 
of  the  summary  due  to  Professor  Crum  Brown.1  "  Liquid  water, 
quite  free  from  dissolved  gases,  does  not  act  on  iron  at  ordinary 
temperatures.  At  high  temperatures,  very  rapidly  at  a  red  heat, 
iron  is  oxidised  by  water  or  water  vapour,  and  is  converted  into 
the  magnetic  oxide  of  iron.  This  magnetic  oxide  is  found  on 
the  surface  of  the  iron  as  an  adherent  coating,  and  only  when  it 
is  detached  can  the  water  gain  access  to  lower  layers  of  the 
iron. 

"  Oxygen  gas  alone  does  not  act  at  ordinary  temperatures  on 
iron.  At  high  temperatures  it  also  converts  the  iron  into  the 
magnetic  oxide  which  forms  an  adherent  coating.  The  same  is 
the  case  with  carbonic  acid  gas,  acting  alone.  At  ordinary 
temperature  it  is  without  action.  At  high  temperatures  the 
carbonic  acid  is  reduced  to  carbonic  oxide,  and  the  iron  is 
oxidised  to  magnetic  oxide,  which  forms  an  adherent  coating." 

Liquid  water  with  oxygen  dissolved  in  it  will  not  act  at 
ordinary  temperatures  on  iron  if  lime  be  in  solution,  or  any 

'Jour.  Iron  and  Steel  Inst.,  Vol.  ii.,  1888,  pp.  129-131.  See  also  Trans, 
Inst.  N.  A.,  Vol.  xiii.,  pp.  95,  96. 


THE  MODERN  STEAM  BOILER.  337 

caustic  alkali  which  is  capable  of  combining  with  carbonic 
acid,  and  is  itself  without  action  on  iron.  But  "  when  the 
lime  or  caustic  alkali  has  been  converted  by  the  carbonic 
acid  of  the  air  into  carbonate,  then  "  free  carbonic  acid  can  be 
absorbed  from  the  air,  and  rusting  will  begin. 

"  Water,  containing  carbonic  acid  dissolved  in  it,  acts  on  iron 
at  ordinary  temperatures,  forming  ferrous  carbonate,  which 
dissolves  in  the  carbonic  acid  water,  forming,  no  doubt,  ferrous 
bicarbonate.  In  this  action  hydrogen  gas  is  given  off.  If 
oxygen  is  present,  dissolved  in  the  water,  it  will  unite  with  the 
nascent  hydrogen  ;  and  if  we  have  sufficient  water,  iron  and 
carbonic  acid,  the  whole  of  the  dissolved  oxygen  will  thus  be 
consumed.  The  presence  of  dissolved  oxygen  quickens  the 
solution  of  the  iron,  the  tendency  of  the  oxygen  to  combine 
with  the  nascent  hydrogen  supplying  an  additional  moiive  to  the 
action.  Probably  in  ordinary  rusting  no  hydrogen  actually 
becomes  free,  as  under  ordinary  conditions  there  will  always  be 
enough  dissolved  oxygen  to  convert  all  the  nascent  hydrogen 
into  water. 

"  When  a  solution  of  ferrous  bicarbonate  is  exposed  to  an 
atmosphere  containing  neither  free  oxygen  nor  carbonic  acid,  it 
loses  carbonic  acid,  and  insoluble  ferrous  carbonate  is  precipi- 
tated. If  free  oxygen  is  present  in  the  atmosphere  to  which  it 
is  exposed,  the  ferrous  carbonate  is  oxidised  to  ferric  hydrate, 
carbonic  acid  being  given  off.  This,  if  the  water  is  not  already 
saturated  with  carbonic  acid,  dissolves  in  the  water."  In  this 
way  the  carbonic  acid  is  not  used  up  in  the  process,  but  is  re- 
peatedly set  free,  and  becomes  ready  to  act  on  a  new  surface  of 
the  metallic  iron.  "  The  continuation  of  the  process  of  rusting 
is  not,  therefore,  dependent  on  new  carbonic  acid  absorbed 
from  the  air,  but  the  original  carbonic  acid,  if  not  removed,  can 
carry  on  the  process  indefinitely,  as  long  as  liquid  water 
is  present,  and  oxygen  is  supplied  from  the  air.  Once 
the  process  is  started  it  goes  on  more  rapidly,  because  the 
porous  rust  not  only  does  not  protect  the  iron,  but  favours  by 
its  hygroscopic  character,  the  condensation  of  water  vapour  from 
the  air  as  liquid  water." 

It  is  to  be  observed  here  that  the  gases  referred  to,  vi/., 
oxygen  and  carbonic  acid,  are  dissolved  in  the  water  and  are  in  a 
very  different  state  from  liquid  oxygen  and  liquid  carbonic  acid, 


338  THE  PRACTICAL  PHYSICS  OF 

which  can  be  produced  only  at  an  extremely  low  temperature. 
It  is  therefore  a  mistaken  idea l  which  has  been  expressed  that 
as  dissolved  "  they  are  in  the  true  liquid  state,  and  behave  in 
every  way  as  liquids."  On  the  contrary,  they  remain  in  solution 
at  temperatures  far  above  those  at  which  these  gases  exist  as 
liquids,  and  are  liberated  by  heat  from  the  water  before  it 
becomes  vapourized.  It  is  a  further  mistake  to  apply  the  term 
"  nascent  "  to  the  oxygen  which  thus  is  liberated  from  solution — it 
has  not  changed  its  condition  ;  it  was  absorbed  as  free  oxygen  and 
is  liberated  in  the  same  state.  To  have  nascent  oxygen  we  should 
require  some  chemical  action  or  decomposition  as  the  result  of 
which  oxygen  that  was  formerly  in  chemical  combination  is 
liberated.  The  oxygen  and  carbonic  acid  held  in  suspension  by 
water  or  dissolved  in  it  are  liberated  by  boiling  the  water,  and 
the  same  result  follows  when  the  water  is  placed  under  the 
receiver  of  an  air-pump,  and  the  atmospheric  pressure  is  removed. 
Consequently  carbonic  acid  and  oxygen  dissolved  in  water  are 
not  "  put  into  the  nascent  state  by  the  heat  transmitted  through 
the  metal  to  the  water,"  any  more  than  they  are  by  being 
set  free  under  the  air-pump  ;  and  as  we  have  seen  from  Dr. 
Crum  Brown's  summary,  their  action  upon  iron  or  steel  is 
not  dependent  upon  such  an  explanation. 

Absorption  of  Gases  by  Liquids. — Of  more  interest  than  any 
such  crude  theoretical  notions  are  the  questions  of  the  rate  of 
absorption  of  these  gases  in  water,  and  the  conditions  of  their 
liberation  therefrom. 

In  general  the  amount  of  a  gas  absorbed  by  a  liquid  upon 
which  it  exerts  no  direct  chemical  action,  depends  on  the  specific 
nature  of  the  gas  and  that  of  the  liquid,  regulating  the  degree  of 
solubility  of  gases  in  different  liquids,  on  the  temperature  of  the 
liquid  and  gas,  and  on  the  pressure  under  which  absorption 
takes  place. 

With  few  exceptions,  the  volume  of  gas  absorbed  by  a  liquid 
decreases  with  increase  of  temperature,  and  increases  with  a 
fall  of  temperature.  It  has  been  said2  that  "  in  the  case  of  many 
of  the  less  soluble  gases,  the  alteration  in  the  absorbed  volume 
effected  by  changes  of  temperature  lying  within  the  range  of 

1  "  Steam     Engine     Boiler     Feeding,"    by    James     Weir.      International 
Engineering  Congress,  Chicago,  1893. 
'    2  "  Watts'  Diet,  of  Chemistry,"  Vol.  ii.,  p.  791. 


THE  MODERN  STEAM  BOILER. 


339 


easy  experimentation  is  so  small  that  it  can  only  be  detected  by 
accurate  observation.  Indeed,  the  earlier  chemists,  especially 
Dalton,  believed  that  the  amount  of  gas  absorbed  was  entirely 
independent  of  the  temperature."  As  regards  the  influence  of 
pressure,  it  has  been  found  that  within  the  limits  of  the  strict 
application  of  Boyle's  law  (that  the  volume  of  a  gas  is  inversely 
proportional  to  the  pressure  to  which  it  is  subjected),  the  quan- 
tity or  weight  of  gas  absorbed  by  liquid  varies  directly  as  the 
pressure,  so  that  under  equal  circumstances  of  temperature  more 
gas  is  absorbed,  as  the  pressure  is  greater. 

In  order  to  compare  the  solubility  of  various  gases  in  liquids, 
the  volume  of  gas  (measured  at  standard  temperature,  o°  C.,  and 
pressure,  76  mm.  of  mercury),  which  is  absorbed  under  a  pres- 
sure of  76  mm.  of  mercury  in  one  volume  of  liquid  at  the 
temperature  of  observation,  is  determined,  and  this  volume  is 
called  the  coefficient  of  absorption  of  that  gas  in  that  liquid. 

Coefficients  of  Absorption. — These  coefficients  have  been  for 
the  most  part  determined  by  Bunsen  and  his  pupils,  and  the 
following  are  amongst  their  results  : — 

TABLE  LXV. 


Gas. 

Coefficients  of  Absorption  in  Water. 

At  o°  C. 

At  20°  C. 

Nitrogen     

0-02035 
17967 
0-04114 
0-02471 

0-01403 
0-9014 
0-02838 
0-OI704 

Carbonic  Acid 

Oxygen 

Atmospheric  Air       

The  effects  of  variation  of  pressure  and  of  temperature  are 
still  further  shown  in  the  coefficients  of  absorption  of  ammonia 
in  water  ascertained  by  Roscoe  and  Dittmar.  The  weight  in 
grammes  of  ammonia  absorbed  i by  i  gramme  of  water  at  o°  C. 
under  variation  of  direct  i  pressure  expressed  in  metres  of  mercury 
was  : — 

At  o'oi  m.  =  0-044  gram.  ;  at  070  m.= 0*840  grm  ;  at  roo  m.= 
1*037  grm-  J  at  I'5°  m.  =  1-526  grm.  ;  and  at  2*0  m.=2T95  grm. 


340  THE  PRACTICAL  PHYSICS  OF 

Under  a  constant  barometric  pressure  of  076  m.  the  quantity 
absorbed  under  variation  of  temperature  was  at  o°  C.= 0*875 
grm.  ;  at  24°  C.  =  0-474  £rm-  I  anc^  at  5°°  C.=o-i86  grm. 

Limits  of  Pressure  used. — Roscoe  has  remarked  that  the  experi- 
ments which  have  been  made  to  verify  the  law  of  pressures 
have  been  applied,  not  so  much  to  the  determination  of  the 
exactitude  of  the  law  under  high  pressures,  as  to  the  exemplifi- 
cation of  the  truth  of  the  law  of  partial  pressures.  Thus  the 
solubility  of  carbonic  acid  under  varying  pressures  has  only  been 
examined  by  Bunsen  between  the  limits  of  523  and  725  milli- 
metres of  mercury,  whilst  Henry  employed  a  pressure  of  1-4 
metres  of  mercury. 

The  limits  of  pressure,  therefore,  beyond  which  gases  do  not 
obey  the  law  of  pressure  have  not  as  yet  been  experimentally 
ascertained  in  many  cases.  The  law,  it  appears,  is  not  strictly 
applicable  in  the  case  of  the  more  soluble  gases  within  ranges  of 
pressure  varying  from  o  to  2  atmospheres.  Experiments  made 
in  Sir  H.  Roscoe's  laboratory  showed  that  under  direct  variation 
of  pressure  of  from  0*050  to  2-5  metres  of  mercury,  the  quantity  of 
ammonia  dissolved  in  water  at  all  temperatures  below  100°  C.  is 
not  directly  proportional  to  the  pressure  ;  but  that  the  deviation 
becomes  less  as  the  temperature  increases,  until  at  100°  C.  the 
law  of  Dalton  holds  good. 

Effects  of  Mixture. — An  admixture  of  different  gases  has  also 
been  found  to  affect  the  degree  of  solubility  of  both  in  water,  so 
that  the  liquid  does  not  dissolve  so  much  of  any  one  of  the  gases 
as  it  would  have  done  if  that  gas  alone  had  been  present.  The 
presence,  therefore,  of  a  foreign  gas  acts  as  the  equivalent  of  a 
direct  diminution  of  pressure. 

Action  of  Water  Vapour. — Roscoe  has  also  noted  the  important 
fact  that  •'  the  vapour  of  water  acts  precisely  as  a  foreign  gas 
would  do  in  reducing  the  partial  pressures  ;  hence  in  all  the 
calculations  of  the  absorption  -  coefficients  of  gases  in  liquids 
determined  chemically,  the  vapour  of  \vater  present  in  the 
atmosphere  of  otherwise  pure  gas  existing  above  the  liquid  must 
be  regarded  as  a  foreign  gas,  which  therefore  alters  the  pressure 
on  the  absorbed  gases.  This  consideration  has  been  attended  to 
in  but  few  of  the  chemical  determinations  yet  made  of  the  more 
oable  g ases." 

Conditions  of  Escape  of  Gases. — The  gases  which  are  absorbed 


THE  MODERN  STEAM  BOILER.  341 

in  a  liquid  in  accordance  with  Dalton's  law  are  completely 
liberated  from  that  liquid  when  the  conditions  are  such  that  the 
pressure  on  the  absorbed  gases  is  reduced  to  zero.  This  result 
may  be  produced  in  either  of  the  following  ways  :  (i)  By 
actually  removing  all  pressure,  except  that  of  the  tension  of  the 
liquid,  by  evacuation  under  the  receiver  of  an  air-pump  ;  (2)  by 
placing  the  saturated  liquid  in  an  atmosphere  of  a  gas  different 
from  any  of  those  absorbed  ;  (3)  by  bringing  the  liquid  to  the 
boiling  point  and  continuing  the  ebullition  ;  and  (4)  by  passing 
a  foreign  gas  or  vapour  through  the  liquid — this  last  being,  as 
Roscoe  says,  equivalent  to  boiling. 

Gases  are  also  set  free  on  the  solidification  of  liquids  which 
have  absorbed  them,  but  that  does  not  bear  upon  their  action  on 
steam  boilers  except  as  also  disproving  the  "  liquid  "  gas  theory. 

These  facts,  however,  show  that  Mr.  N orris's  l  deductions  as  to 
the  presence  of  gases  in  boilers  under  high  pressures  of  steam 
are  not  well  founded,  and  his  theory  of  their  presence  in  layers 
above  the  water  cannot  be  upheld,  on  account  of  the  laws 
of  diffusion.  Apart  from  the  fact  that  no  investigations  on  this 
subject  have  as  yet  been  undertaken  at  anything  like  the  pres- 
sures now  employed  in  steam  boilers,  where  such  pressures  are 
accompanied  by  a  considerable  rise  in  temperature,  the  ascer- 
tained result  that  the  vapour  of  water  acts  as  a  foreign  gas, 
would  prove  that  all  other  gases  must  be  expelled  from  the  water 
of  a  boiler  under  steam.  No  doubt  the  iron  or  steel  of  the 
boiler  may  be  hot  before  the  last  traces  of  the  gases  which  water 
holds  absorbed  are  set  free,  and  so  far  the  power  of  these  gases 
to  act  chemically  on  the  metal  may  be  intensified,  but  it  seems 
certain  that  these  gases  cannot  be  retained  there  whilst  the 
boiler  is  at  work.  It  is  certain  that  they  enter  in  the  wrater  with 
which  the  boiler  is  filled  at  starting,  and  that,  unless  precautions 
are  taken,  fresh  quantities  may  return  to  the  boiler  with  the 
feed-water,  even  though  it  be  produced  from  condensed  steam. 

Rate  of  Absorption. — But  here  we  are  without  data  to  guide 
us  as  to  the  quantity  which  is  likely  thus  to  be  readmitted, 
because  there  are  no  experimental  data  available  to  show  the 
rate  at  which  gases  are  absorbed  by  liquids  under  varying 
conditions  of  temperature  and  pressure.  The  quantitv  absorbed 

1  Trans.  Inst.  Xuval  Architects,   Vol.  xxiii.,  pp.  154-158. 


342  THE  PRACTICAL  PHYSICS  OF 

has  been  investigated,  and  it  has  been  found  that  rain  water, 
which  is  necessarily  the  purest  of  natural  waters,  contains  in  one 
gallon  about  7  cubic  inches  of  gas,  containing  from  20  to  30  per 
cent,  of  oxygen,  60  to  70  per  cent,  of  nitrogen,  and  5  to  10  per 
cent,  ot  carbonic  acid.  The  water  of  Loch  Katrine  has  been 
found  to  contain  7  to  8  cubic  inches  of  gas  to  the  gallon,  of 
which  about  3  cubic  inches  are  oxygen.  It  will  be  noticed  that 
the  proportions  in  which  the  various  gases  exist  in  water  are  not 
the  same  as  their  proportions  in  the  atmosphere,  but  they  are  in 
accordance  with  the  relation  existing  between  the  coefficients 
of  absorption  of  these  gases  in  water  and  their  percentage 
quantities  in  the  atmosphere.  It  has  been  found  that  sea-water 
holds  in  solution  a  larger  proportion  of  carbonic  acid  than  fresh 
water  does,  and  this  has  been  shown  by  J.  Y.  Buchanan  to  be 
due  to  the  sulphates  which  sea- water  holds  also  in  solution.  (See 
Appendix  III.,  pp.  611-626.; 

As  to  how  long  it  takes  for  water  to  absorb  a  given  quantity  of 
gas,  we  have  as  yet  no  certain  data.  Judging  from  the  quantity 
of  oxygen  absorbed  by  the  blood  and  the  limited  time  of  contact 
between  the  gas  and  the  liquid  in  the  process  of  respiration,  it  is 
probable  that  absorption  is  a  very  rapid  process.  It  is,  however, 
unsafe  to  draw  any  rigid  parallel  between  blood  and  water, 
inasmuch  as  the  action  in  the  case  of  the  blood  is  not  merely  a 
chemical  one,  but  is  complicated  by  the  fact  that  it  is  an  organic 
action,  and  we  have  no  equivalent  in  physics  for  vital  energy. 

More  nearly  allied  to  our  subject  is  the  absorption  of  gases  in 
the  manufacture  of  aerated  waters,  but  even  from  this  source 
there  is  little  information  to  be  derived.  The  absorption  of  gas 
in  this  manufacture  takes  place  under  considerable  pressure, 
with  the  assistance  of  a  lowr  temperature  and  more  or  less  agita- 
tion of  the  liquid.  Moreover,  as  it  is  desired  to  have  waters 
fully  charged  with  gas,  some  little  time  is  always  allowred  to 
elapse  before  the  exposure  of  the  wrater  to  the  pressure  of  gas 
terminates  by  the  operation  of  bottling.  In  using  the  domestic 
gazogene  also,  it  is  always  necessary  to  allow  an  interval  of  one 
to  two  hours  after  the  operation  of  charging  before  properly 
aerated  water  can  be  obtained.  But,  here  again,  we  are  dealing 
writh  water  which  is  to  be  so  fully  charged  writh  gas  under 
pressure  that  it  will  effervesce  on  exposure  to  the  atmosphere. 
The  presumption  is  that  the  amount  of  gas  which  water  will  hold 


THE  MODERN  STEAM  BOILER.  343 

at  atmospheric  pressure  is  absorbed  very  rapidly.  A  simple 
experiment  throws  light  on  this  point.  Let  a  glass  tube  half 
filled  with  water  be  sealed  up  by  means  of  the  blow-pipe  whilst 
the  water  it  contains  is  boiling  and  steam  is  issuing.  When  cold, 
the  metallic  click  of  the  "  water  hammer  "  will  show  that  the 
water  and  the  tube  are  deprived  of  air — there  is  a  vacuum  in  the 
tube.  Now  let  the  sealed  end  of  the  tube  be  opened  under  the 
surface  of  ordinary  drinking  water  in  a  glass  vessel,  and  a  very 
interesting  phenomenon  will  be  witnessed.  It  might  be  supposed 
that  the  water  from  the  outside  would  at  once  rush  into  the  tube 
to  fill  up  the  vacuous  space,  but  that  does  not  happen.  Instead 
of  that,  the  water  in  the  glass  vessel  suddenly  becomes  violently 
effervescent,  bubbles  of  air  appearing  in  all  portions  of  it  and 
rushing  in  every  direction  and  even  downwards  to  the  unsealed 
end  of  the  tube,  into  which  no  water  enters  until  a  state  of 
equilibrium  has  apparently  been  established  between  it  and  the 
water  outside  it  in  the  matter  of  the  gas  contained  by  each. 
Thereupon,  the  water  rushes  in  and  completely  fills  up  the  tube. 
All  this  takes  place  in  a  few  seconds,  and  it  is  proof  of  the 
rapidity  with  which  absorption  of  gas  can  take  place. 

Effects  of  Temperature  and  Pressure. — It  wras  discovered  by 
Mr.  R.  Mallet  that  corrosion  proceeds  faster  in  fresh  water 
which  contains  air,  or  is  in  contact  with  air,  at  temperatures  of 
175°  to  about  190°  F.  than  at  atmospheric  temperatures,  and  that 
in  heating  such  water  up  to  212°,  air  is  evolved  from  it  most 
freely  at  190°  to  195°  F.,  so  that  there  is  a  direct  relation  between 
the  rapidity  of  corrosion  and  the  liberation  of  air.  Mr.  Mallett 
held  that  the  rapidity  of  corrosion  is  in  the  direct  ratio  of  the 
volume  of  air  set  free  at  any  given  temperature,  because  the 
attraction  of  the  water  for  the  air  being  destroyed,  the  air  is  then 
free  to  attack  the  metal.  This  observation  also  serves,  to  some 
extent,  to  illustrate  the  part  played  in  boiler  corrosion  by  the 
high  temperatures  which  are  usually  present.  It  is  well  known 
that  chemical  affinity  is  directly  affected  by  temperature,  so 
that  some  substances  which  are  inert  towards  one  another  in  the 
cold,  or  at  ordinary  atmospheric  temperature,  produce  active 
reactions  when  heated  in  contact.  In  general  also,  chemical 
action  which  exists  at  ordinary  temperature  is  intensified  by 
elevation  of  temperature. 

Increase   of    pressure — sometimes  even  without   addition  of 


344  THE  PRACTICAL  PHYSICS  OF 

heat — also  produces  active  chemical  action  in  some  cases.  We 
have  an  instance  of  this  in  the  mutual  decomposition  of  the 
magnesia  salts  and  carbonate  of  lime  in  sea-water,  which  is 
referred  to  at  page  613  of  Appendix  III. 

Influence  of  Points. — There  is  a  natural  phenomenon,  which 
without  doubt  exerts  some  influence  upon  the  direction  in  which 
corrosive  action  is  developed,  and  that  is  the  effect  produced  by 
points  on  the  metal  surfaces.  It  is  well  known  that  if  water  be 
boiled  in  a  vessel  having  a  perfectly  smooth  and  clean  inside 
surface  the  steam  does  not  rise  in  a  steady  flow  of  bubbles,  but 
is  produced  spasmodically  and  leaves  the  surface  in  sudden, 
violent  and  intermittent  outbursts.  To  cure  this  violent  action 
it  is  sometimes  necessary  to  introduce  into  the  vessel  a  little  fine 
sand,  the  grains  of  which  at  once  act  as  nuclei  for  the  formation 
and  escape  of  steam  bubbles,  which  rise  from  them  in  a  quiet 
and  continuous  stream.  A  similar  effect  is  seen  where  little 
grains  even  of  cork  are  floating  in  an  effervescing  liquid — the 
floating  specks  are  points  at  which  the  bubbles  of  gas  are  seen 
to  form  and  from  which  they  escape. 

The  discharge  of  electricity  !  into  or  through  a  medium  offering 
some  resistance  is  also  determined  from  points,  and  this  is  clearly 
analogous  to  the  flow  of  steam  or  heat  noticed  above. 

Such  phenomena  render  it  easy  to  understand  how  2  "  the 
rusting  of  the  purest  iron  in  the  form  of  the  most  uniform  or 
even  polished  surfaces  of  a  plate,  always  initiates  at  points." 
These  may  spread  and  finally  coalesce  or  the  action  may  proceed 
more  rapidly  into  the  plate  than  over  its  surface,  in  which  latter 
case  we  have  that  form  of  corrosion  called  "  pitting,"  or,  as  in 
R.  Mallet's  papers,  according  to  French  chemists,  "  tubercular 
corrosion."  "  Even  were  the  iron  itself  perfectly  homogeneous," 
remarked  Mr.  Mallet,  "  rust  would  set  in  thus  at  points,  for  the 
action  is  determined  to  any  point  touched  by  another  solid, 
which  may  be  a  neutral  one  (chemically),  such  as  glass,  or 
porcelain,  or  wood." 

Xo  n- uniformity  of  Texture. — Microscopical  examinations  of 
steel  and  iron,  such  as  those  of  Dr.  Sorby,3  Professor  Roberts- 

1  See  Min.  Proc.  Inst.  C.  K.,  Vol.  cxv.,  p.  484. 
3  Trans.  Inst.  X.A.,ATol.  xiii.,  p.  96. 

3  Jour.  Iron  and  Steel  Inst.,  Vol.  i.,  1887,  p.  255;  Min.  Proc.  Inst.  C.E., 
xcv.,  144  ;  Jour.  Soc.  of  Arts,  Oct.  29,  1897. 


THE  MODERN  STEAM  BOILER.  345 

Austen,  Professor  Arnold,  and  others,  have  revealed  the  fact  that 
there  is  complexity  of  structure  in  the  finest  of  such  metals,  so  that 
there  need  be  no  difficulty  in  our  perceiving  why  the  chemical 
action  of  corrosion  begins  at  points,  even  when  there  is  no  speck 
of  mill  scale  or  of  slag  present  at  or  near  the  surface.  The 
presence  of  a  high  temperature  intensifies  such  action,  and  this 
of  itself  would  be  enough  to  show  that  the  opinion  frequently 
expressed,  that  "  pitting  must  be  least  where  the  water  circula- 
tion is  greatest,"  must  be  wrong,  as  also  the  experience  of  pitting 
in  the  boilers  of  the  s.s.  "  Propontis  "  and  in  other  water-tube 
boilers,  has  repeatedly  shown.  In  these  cases  the  pitting  has 
been  greatest  in  the  small  tubes  or  surfaces  nearest  to  the  fire, 
the  formation  of  steam  and  movement  of  the  water  being  greatest 
there  also. 

Thinness. — Another  fact  was  noticed  by  Mallet,1  the  accuracy 
of  which  experience  with  boilers  has  frequently  confirmed,  viz., 
that  thin  material  corrodes  proportionately  faster  than  metal  in 
thicker  pieces.  The  rapidity  with  which  the  thin  tubes  of 
water-tube  and  other  boilers  have  often  been  eaten  through  has 
been  a  source  of  surprise  to  those  who  did  not  understand  the 
nature  of  the  action  taking  place. 

Effects  of  Oils. — The  action  and  effects  of  oily  matters,  and 
their  share  in  promoting  corrosion,  have  been  the  subject  of 
all  shades  of  opinion,  from  the  incredulity  which  has  denied 
the  possibility  of  their  producing  any  action,  to  the  dogmatism 
which  has  insisted  that  all  corrosive  action  must  be  due  to  them. 
There  are,  of  course,  intermediate  shades  of  opinion  which 
display  a  more  intelligent  acquaintance  with  the  facts  of  the 
case,  and  there  is  no  doubt  that  different  instances  of  boiler 
corrosion  have  furnished  evidence  of  variation  in  the  extent  to 
which  the  action  of  oils  may  proceed. 

It  is  at  once  apparent  that  we  must  have  widely  different 
groups  of  phenomena  according  as  we  are  dealing  either  with 
tallow  or  animal  and  vegetable  oils  on  the  one  hand,  or  with 
mineral  oils  on  the  other.  The  fats  and  oils  of  the  one  class 
have  as  the  basis  of  their  constitution,  palmitic,  oleic,  and  stearic 
acids,  into  which  (writh  glycerine)  they  can  be  broken  up  by  the 
action  of  heat,  and  all  the  more  readily  in  presence  of  the 

1  See  Report,  No.  2,  p.  236. 


34^  THE  PRACTICAL   PHYSICS  OF 

alkaline  earths,  such  as  lime,  potash,  or  soda.  Such  decompo- 
sition would  take  place  partly  in  the  cylinders  of  the  steam 
engine,  but  more  extensively  in  the  boiler,  where  saponification 
would  be  possible. 

Mineral  lubricating  oils  consist  of  hydro-carbon  compounds, 
whose  specific  gravity  ranges1  from  '865  to  about  '910,  probably 
anthracene,  chrysene,  pyrene,  etc.  They  are  not  liable  to  any 
such  decomposition  as  can  take  place  with  oils  and  fats  of  the 
first  class,  but  may  be  volatilised  at  a  high  temperature,  or 
partially  volatilised  and  partly  reduced  to  a  deposit  of  solid 
carbonaceous  material. 

These  two  classes  of  lubricants  should  not  be  confounded,  but 
it  frequently  appears  in  papers  on  boiler  corrosion  that  there  is 
some  confusion  regarding  them  existing  in  the  minds  of  engi- 
neers. Perhaps  the  reason  of  this  is  to  be  found  in  the  fact 
which  was  insisted  upon  by  Mr.  J.  B.  Dodds,  in  the  paper 
referred  to  (p.  325,  ante),  that  in  commerce  the  so-called  mineral 
lubricating  oil,  or  "  cylinder  oil,"  is  seldom  to  be  obtained  pure, 
but  is  frequently  adulterated  with  vegetable  and  animal  oils. 
Some  analyses2  seem  to  bear  this  out.  If  so,  the  remedy  is 
simple,  for  there  should  be  no  difficulty  nowadays  in  buying  oil 
according  to  a  guaranteed  analysis,  or  in  analysing  a  specimen 
of  the  material  which  is  sold  and  delivered  for  pure  mineral 
lubricating  oil. 

The  action  of  animal  and  vegetable  oils  in  connection  with 
boiler  corrosion  has  frequently  been  exemplified. 

In  Appendix  III.  (pages  618  and  619),  and  in  the  paper  by 
Mr.  Jas.  Gilchrist,  referred  to  in  the  same  appendix  (page  623), 
there  are  details  given.  Other  cases  are  reported  by  Mr.  H. 
Hallett,  Mr.  Sinclair  Couper  and  Mr.  J.  B.  Dodds  in  the  papers 
referred  to  (p.  325,  ante). 

Undecomposed  grease,  unless  arrested  by  filtering,  can  carry 
particles  of  brass,  copper,  or  other  foreign  material  into  the 
boiler,  adding  to  the  elements  of  danger  there. 

The  fatty  acids  in  contact  with  brass  and  copper  undoubtedly 
corrode  these  .metals,  so  that  particles  of  copper  separated  by 
attrition,  or  chemical  action,  or  both,  have  often  been  carried 

1  See     a    Manualette    of    Destructive    Distillation,    by    E.   J.    Mills,    D.Sc., 
F.R.S. 
1  Trans.  Inst.  E.  and  S.  in  Scotland,  Vol .  xl .,  pp.  103,  104. 


THE  MODERN  STEAM  BOILER.  347 

into  boilers.  The  fact  that  Mr.  Weston  !  could  not  find  a  trace 
of  copper  /';/  solution  in  the  water  of  a  boiler  furnishes  no 
evidence  to  the  contrary,  because  any  salt  of  copper  formed  in 
such  circumstances  would  be  quickly  decomposed  by  electrolysis, 
and  therefore  the  proper  place  in  \vhich  to  look  for  the  presence 
of  copper  would  be  in  the  solid  deposits  of  the  boiler.  In  such 
deposits  traces  of  copper  have  frequently  been  found 2  by  analysis. 

When  a  soapy  emulsion,  due  to  the  presence  of  oil,  has 
not  been  formed  in  boilers,  producing  the  evils  of  priming, 
the  soap  resulting  from  the  saponification  of  oil  or  grease  has 
been  found  to  form  first  a  scum  on  the  water  surface  and  after- 
wards, by  becoming  loaded  with  mineral  matters  and  sinking  in 
pieces,  a  scale  on  the  heating  or  other  surfaces  of  the  boiler 
promoting  both  corrosion  and  overheating. 

Remedy. — The  remedy  for  all  this  is  to  use  only  pure  mineral 
oil  for  lubricating  cylinders,  piston  rods,  and  pumps  in  both 
main  and  feed  engines. 

The  possibilities  of  damage  from  this  oil,  if  it  is  pure,  are  few, 
and  are  practically  confined  to  the  formation  of  a  coating  or 
deposit  on  the  heating  surfaces  of  the  boiler.  Where  the 
surfaces  become  covered  with  the  oil  alone  the  chances  of  over- 
heating are  small,  as  the  experiments  recorded  in  Chapter  IV. 
prove.  It  is,  however,  possible  to  have  the  oil  combined 
mechanically  with  solid  particles,  as  has  been  pointed  out  by 
Professor  Lewes,3  according  to  an  action  familiar  to  chemists  in 
connection  with  precipitation  and  filtration  (see  Appendix  III., 
p.  619),  and  in  such  cases  the  chances  of  damage  from 
the  deposit  causing  overheating  are  much  more  serious.  The 
entrance  of  oil  into  the  boiler  is  probably  not  entirely  prevented, 
even  by  the  use  of  filters,  for  Professor  Lewes  has  shown  by  an 
interesting  experiment  that  a  pure  mineral  lubricant  called 
"  Valvoline,"  having  a  specific  gravity  of  '889  and  boiling  at 
371°  C.  (or  699°  F.),  was  carried  over  by  a  current  of  steam  at 
a  much  lower  temperature  than  is  common  in  marine  boilers. 
"  A  retort  containing  valvoline  was  carefully  heated  over  a  sand- 
bath,  its  temperature  being  ascertained  by  a  thermometer,  and 

1  Trans.  I.  X.  A.,  Vol.  xxiii.,  p.  153. 

2  Trans.  Inst.   E.  and  S.  in  Scotland,  Vol.  xlii.,  p.    lo,  Part  v.,  and  Vol.  xl., 
T-52. 

3  Trans.  Inst.  N.  A.,  1891. 


348  THE  PRACTICAL  PHYSICS  OF 

steam  was  then  blown  through  it,  with  the  result  that  at  248°  F. 
or  120°  C.,1  the  steam  became  'greasy  'and  the  oil  commenced 
to  pass  over  with  it."  This  of  itself  does  not,  of  course,  explain 
how  the  oil  gets  into  a  marine  boiler,  because,  as  a  matter  of 
fact,  no  steam,  either  "  greasy  "  or  not  greasy,  is  passed  into  that 
vessel.  But  the  experiment  shows  that  the  oil  may  be,  at  a 
comparatively  high  temperature,  readily  separated  by  steam  into 
extremely  fine  particles  which  may  pass  along  with  the  feed 
water  through  a  filter,  especially  if  the  filtering  medium  has 
become  slightly  oily  on  the  surface.  Under  these  circumstances 
a  milky  appearance  in  the  water  would  show  the  presence  of  oil, 
but  such  milkiness,  if  due  to  oil,  is  readily  tested  by  the  addition 
of  ether,  which  clears  it. 

There  is  no  reason,  however,  why  the  admission  of  solids  to 
the  boiler  should  not  be  entirely  prevented.  Now  that  feeding 
with  sea-water  is  abolished  in  all  good  marine  practice,  and  the 
loss  of  water  during  a  voyage  is  made  up  by  the  use  of  evapo- 
rators or  distilling  apparatus,  whilst  all  the  feed-water  passes 
through  a  filter  such  as  those  shown  in  Figs.  142,143,  144,  before 
reaching  the  boiler,  we  have  only  the  preliminary  filling  up  with 
natural  fresh  water  to  consider  as  a  possible  breach  in  the 
defence  of  the  boiler.  In  this  case,  if  water  of  the  purity  of 
rain  water  cannot  be  obtained  for  filling  up  the  boiler  before 
a  voyage,  any  salts  of  lime,  soda  or  magnesia  which  the  water 
which  is  employed  contains,  should  be  removed  by  a  pre- 
liminary precipitation  and  filtration,  before  the  water  is 
admitted  to  the  boiler.2  Thereafter  and  during  work,  as  we 
have  seen,  the  entrance  of  fresh  quantities  of  solids  can  be 
prevented. 

It  is  not  likely  that,  where  filters  are  used,  and  economy  in 
the  use  of  lubricating  oil  is  practised,  a  quantity  of  oil  can  pass 
into  the  boilers  sufficient  to  form  an  oily  scum  on  the  surface 
of  the  water.  But  if,  through  some  defect  in _  the  filter,  that 
result  should  occur,  it  wrill  cause  trouble  in  the  working  of  the 
boiler,  and  should  be  removed  by  blowing  off. 

1  This  temperature  corresponds  to  a  steam    pressure   of  only  30  Ibs.  per 
square  inch. 

2  On  this  point  consult  Report  XV.,  uOn  the  Purification  of  the  Feed-water 
of  Locomotives,"  presented  by  J.  A.  F.  Aspinall  to  the  International  Railway 
Congress.     Sixth  session.     Paris,  1900. 


THE   MODERN   STEAM  BOILER. 


349 


350 


THE  PRACTICAL  PHYSICS  OF 


Action  of  Magnetic  Chloride. — The  disuse  of  sea- water  for 
feeding  or  for  making  up  the  feed-water  in  marine  boilers  has 
removed  several  causes  of  destructive  action,  such  as  the  de- 
composition of  magnesic  chloride  and  the  presence  of  an 
additional  quantity  of  carbon-dioxide  liberated  from  sea-water , 


7///,/  S 


FIG.    144. 

which  are  noticed  in  Appendix  III.1  and  do  not  need  to  be 
further  dealt  with.  But  it  may  be  remarked  that  as  regards  the 
decomposition  of  magnesic  chloride  and  resulting  reactions, 
hasty  inferences  have  frequently  obstructed  a  clear  understand- 
ing of  the  matter.  It  was  inferred  that  if  by  the  decomposition 

1  See  also  paper  by  J.  B.  Dodds,  in  Trans.  N,  E,  Coast  Inst.  of  Engineers, 
Vol.  v.,  p.  195. 


THE   MODERN  STEAM  BOILER.  351 

referred  to,  hydrochloric  acid  was  set  free,  the  presence  of  this 
acid  ought  to  be  indicated  by  acidity  in  the  water  of  the  boiler  ; 
whereas  its  action  on  the  iron  must  always  have  been  practically 
simultaneous  with  its  liberation  from  the  magnesic  chloride,  so 
that  instead  of  the  \vater  showing  an  acid  reaction  it  was  more 
likely  to  become  alkaline  by  neutralisation  of  the  hydrochloric 
acid  and  accumulation  of  magnesic  oxide.  It  was  also  argued 
that  if  the  iron  were  attacked  by  hydrochloric  acid,  chloride  of 
iron  ought  to  appear  in  the  deposits  found  in  boilers.  But  that 
objection,  like  other  arguments,  was  anticipated  some  years 
before  it  was  made,  by  the  paper  reprinted  in  Appendix  III. 
(p.  625)  in  the  statement  that  oxide,  and  not  chloride,  of  iron 
finally  results  from  the  action.  This  was  also  subsequently 
demonstrated  by  Mr.  J.  B.  Dobbs  (in  Trans.  N.  E.  Coast  Inst.  of 
Engineers  and  Shipbuilders,  Vol.  v.,  pp.  196,  197,  247).  Due 
weight  was,  moreover,  seldom  given  to  the  fact  of  the  presence 
of  a  larger  quantity  of  carbon  dioxide  in  salt  than  in  fresh  water, 
a  great  part  of  this  carbon  dioxide  being  liberated  from 
the  sea-water  by  the  mere  separation  of  the  sulphates 
which  it  holds  in  solution.  These  various  phenomena,  how- 
ever, explain  ho\v  chemical  action  has  been  found  to  proceed 
more  rapidly  in  boilers  which  have  been  partly  fed  with  sea- 
water,  than  in  those  from  which  sea-water  is  carefully  excluded, 
and  they  demonstrate  how  necessary  it  is  that  in  all  marine 
boilers  the  feed  should  be  made  up  with  distilled  water 
alone. 

It  no  doubt  follows  from  this  that  we  must  expect  to  find 
corrosion  at  work  in  distilling  boilers  or  apparatus  used  to  pro- 
duce distilled  from  sea-water.  The  action  of  air  and  carbon 
dioxide  also  show  that  corrosion  may  be  expected  in  feed- 
heaters  which  receive  the  feed-water  either  cold  or  com- 
paratively cold,  where  no  effort  has  been  made  to  keep 
it  denuded  of  air.  Where  such  feed-water  is  delivered  into 
boilers  direct,  without  interposition  of  a  feed-heater,  the  parts 
of  the  boiler  coming  first  into  contact  with  this  water,  on 
its  temperature  being  raised,  must  also  be  exposed  to  corrosive 
actions. 

Delivering  the  feed  into  the  steam  space  is  no  doubt  the  safest 
method  where  air  is  present  in  the  water,  from  the  point  of  view 
of  corrosion,  but  it  is  not  good  in  its  effects  on  circulation,  as  Mr. 


352  THE  PRACTICAL  PHYSICS  OF 

Blechynden's  experiments  prove ' ;  nor  is  it  economical  from  the 
point  of  view  of  heat  transmission. 

It  is  undoubtedly  better  to  have  an  evaporator  or  feed  heater- 
liable  to  corrosion  separate  from  the  boiler,  than  to  expose  any 
part  of  the  boiler  to  this  action,  and  hence  Mr.  Yarrow's  plan  of 
making  some  of  the  tubes  of  his  boiler  do  the  duty  of  a  feed- 
heater  may  lead  to  difficulties  which  more  than  counterbalance 
any  economy  of  heat  obtained  by  this  arrangement.2 

Protective  Measures. — Amongst  the  means  employed  for  the 
protection  of  boiler  surfaces  from  corrosion,  the  action  and 
effect  of  zinc  have  often  been  greatly  over-estimated.  In  fresh 
water  zinc  has  little  protective  power  over  wrought  iron  con- 
sidered electro-chemically,  and  in  sea-water  it  is  readily  oxidised 
by  decomposition  taking  place  in  the  salts  which  that  water 
contains.  With  regard  to  the  action  in  cold  water,  Mr.  Mallet :{ 
wrote  that,  "zinc  is  so  slightly  electro-positive  to  iron  that  its 
protective  power  is  nearly  destroyed  whenever  a  few  spots  of 
rust  have  formed  anywhere  upon  the  iron  with  which  it  is  in 
contact,  the  peroxide  acting  as  an  acid  towards  its  own  base  in 
both  fresh  and  sea- water.  In  the  latter  the  surface  of  the  zinc 
gets  covered  with  a  hard  crystalline  coat  of  hydrated  oxide  and 
of  calc-spar,  which  retards  or  prevents  its  further  corrosion,  and 
thus  permits  the  iron  to  corrode."  In  boiling  water  the  action 
proceeds  much  farther,  and  progesses  rapidly,  so  that  the  zinc 
is  often  quickly  reduced  throughout.  Moreover,  as  commercial 
zinc  is  seldom  pure,  there  are  causes  of  reaction  in  the  constitu- 
tion of  the  metal  itself  which  aid  in  its  disintegration  ;  a  result 
which  amalgamating  its  surface  with  mercury  cannot  prevent. 

It  is  probable  that  the  principal  service  rendered  by  zinc  in 
boilers  has  been  to  provide  a  material  acted  upon  more  readily 
than  the  iron  by  the  acids  set  free  by  the  decomposition  of 
animal  and  vegetable  oils,  and  by  the  oxygen  and  carbon  dioxide 
liberated  on  boiling  the  water.  Mr.  Mallet  stated  that  an  alloy 
of  23  parts  of  zinc  and  8  parts  of  copper  preserves  cast  iron 
from  corrosion  in  cold  water,  and  does  not  waste  itself,  but  it  is 
difficult  to  understand  how  such  a  result  could  be  obtained. 
Protective  action  has  been  claimed  for  devices  such  as  one 


1  See  Chap.  V.,  p.  243,  ante.  2  See  Chap.  V.,  p.  234,  ante. 

3  British  Association  Reports,  1843,  p.  20. 


THE   MODERN  STEAM  BOILER.  353 

called  the  "  Electrogen,"  which  aimed  at  producing  a  galvanic 
current  in  such  relation  to  the  iron  as  constituted  it  the  negative 
element  of  the  couple.  If  this  really  has  a  preservative  effect, 
probably  the  same  result  could  be  more  fully  realised  by  pass- 
ing a  small  current  from  a  dynamo  machine  through  the  boiler. 
At  any  rate  this  is  worth  investigation  in  these  days  in  which  so 
many  steamers  are  fitted  with  electric-lighting  machinery. 

Protective  Coatings. — Efforts  have  also  been  made,  with  some 
degree  of  success,  to  protect  the  iron  of  boilers  by  forming  a 
protecting  coating  on  the  boiler  surfaces,  and  with  a  similar 
object  it  has  also  been  proposed  to  render  the  \vater  innocuous 
to  iron  by  chemical  means.  With  regard  to  the  former  of  these 
plans,  there  are  two  methods  by  which  a  permanent  covering, 
impervious  to  corrosive  action,  can  be  formed.  These  are  the 
process  invented  by  Professor  Barff  and  the  method  suggested 
by  the  author  of  this  work. 

In  Barff' s1  process  a  thin  adherent  coating  of  magnetic  oxide 
is  formed  on  the  iron  by  the  decomposition  of  steam  in  contact 
with  the  metal  at  a  temperature  of  500°  F.,  whilst  in  that  of  the 
author2  a  similar  covering  composed  of  calcium  sulphate  and 
magnesium  hydrate  is  first  deposited  from  fresh  water  and  sub- 
sequently hardened  by  heat.  The  addition  of  lime  preparations 
to  the  water,  in  the  manner  suggested  by  the  author,  would 
render  the  water  "  non-exciting,"  as  Mr.  J.  B.  Dodds3  has 
pointed  out,  and  to  produce  the  same  result  he  proposed  the  use, 
alternatively,  of  a  basic  solution  of  zinc. 

When  not  in  use  boilers  should  be  filled  to  the  top  of  the 
steam  space  with  hot  water  which  has  been  boiled  to  free  it 
from  air,  and  the  boiler  should  then  be  hermetically  closed  and 
kept  in  this  condition  until  it  is  required  for  wrork.  Lime  may 
be  added  to  this  water  or  placed  in  the  boiler,  but  this,  though 
desirable,  should  not  be  necessary  if  the  boiler  has  been 
thoroughly  cleansed  before  being  filled  up  with  the  water. 

"  Another  method  of  preserving  a  boiler  not  in  use  is  to 
empty  it  and  clean  it  thoroughly,  then  close  all  the  manhole 
doors  and  other  openings  except  one  at  the  bottom,  through 

1  See  Jour,  of  Soc.  of  Arts,  February  14,  1877.     Jour.   Iron  and  Steel   Inst. 
Vol.  i.,  1881,  p.  1 66  ;  Vol.  ii.,  1888,  p.  280. 

2  See  Appendix  III.,  pp.  627,  634. 

3  Trans.  N.  E.  Coast  Inst.  of  Engineers,  Vol.  v.,  pp.  198-200. 

N 


354  THE  PRACTICAL  PHYSICS  OF 

which  a  small  stove  full  of  burning  coke  is  put  in,  and  then  the 
bottom  door  is  closed  quickly."  The  object  of  these  methods 
is,  of  course,  to  exclude  moist  air  as  thoroughly  as  possible. 

On  a  review  of  the  subject  it  is  apparent  that  in  good  practice 
the  following  points  should  be  observed  : — 

1.  The   metal  of  which   boilers  are  constructed  should  be  as 

homogeneous  as  possible  in  composition  and  texture.  It 
should  be  well  worked  so  as  to  be  fibrous  rather  than 
crystalline  in  texture,  and  should  not  be  punched  or 
worked  at  a  low  heat.  It  should  be  wrell  annealed  so  as 
to  remove  all  effects  of  local  stresses  and  to  bring  the 
texture  to  a  uniform  condition. 

2.  All  mill  scale  and  dirt  should   be  removed  from  the  sur- 

faces, which  should  also  be  kept  as  free  as  possible  from 
oil. 

3.  All  gases  should  be  removed  from  the  water. 

4.  No  sea-water  should  be  admitted,  and  all  feed- water  should 

be  made  up  with  distilled  water. 

5.  All  feed-water  should  be  passed  through  a  good  filter. 

6.  The  feed-water  should  be  heated  in  feed-heaters  which  are 

separate  in  construction  from  the  boiler. 

7.  The  interior  surfaces  of  the  boiler  should  be  covered  by  a 

thin  protective  coating,  or  the  water  should  be  treated 
chemically  as  above. 

8.  No  vegetable  or  animal  oil  should  be  used  in  any  engines 

connected  in  any  way  with  the  boiler. 

9.  When  not  in  use  boilers  should  be  carefully  protected  from 

deterioration  by  one  of  the  methods  described. 


CHAPTER  VIII. 
HISTORICAL  SKETCH  OF  BOILER  DESIGNS. 

IN  the  production  of  steam  for  other  than  domestic  purposes 
various  kinds  of  vessels  and  modes  of  operating  have  been  tried. 
The  more  ancient  forms  of  boilers  appear  to  modern  eyes  some- 
what grotesque,  and  it  is  certain  that  they  were  not  adapted  for 
continuous  work  of  long  endurance.  They  were,  however,  not 
subjected  to  any  great  stress  of  work.  An  archaic  form  has 
been  described  by  a  writer  in  Engineering  of  nth  January,  1895, 
where  an  illustration  of  it  appears.1  It  was  an  urn-shaped 
vessel  discovered  at  Pompeii. 

Others  will  be  found  in  the  older  wrorks  containing  a  his- 
torical account  of  the  development  of  the  steam  engine,  such  as 
the  writings  of  Stuart,  Farey,  and  Tredgold. 

The  earliest  practicable  boilers  seem  to  have  been  spherical  or 
oval  (sometimes  called  "  ovoid ")  vessels,  but  after  a  time  flat 
surfaces  wrere  introduced  in  the  "  waggon  "  and  similar  forms, 
whilst  other  designs,  more  suited  to  the  production  of  steam  of 
some  degree  of  pressure  above  that  of  the  atmosphere,  soon 
began  to  appear. 

Methods  of  Raising  Steam. — In  the  various  methods  of  raising 
steam  which  have  been  practised,  the  following  arrangements 
have  been  used  : — 

1.  A  compact  body  of  water  enclosed  in  a  vessel  of  spherical, 

cylindrical,  oblong,  or  other  form,  and  heated  from  the 
outside,  either  without  or  with  internal  flues  or  passages. 
This  is  the  tank  or  shell  boiler,  which  has  assumed  many 
shapes,  with  plain  or  spiral  flues  and  even  writh  inverted 
furnaces,  the  latest  developments  of  which  are  the  so- 
called  "  Scotch  "  cylindrical  or  drum  boiler,  the  Lanca- 
shire boiler,  and  the  locomotive  boilers. 

2.  Small  quantities  of  water  projected   successively   on    the 

inner  surfaces  of  a  vessel  kept  at  a  high  temperature  by 

1  See  also  "  Les  Chaud'.eres  Marines,"  by  M.  de  Chasseloup-Laubat.  Paris  : 
1897. 

355  X  2 


356  THE  PRACTICAL  PHYSICS  OF 

tire  applied  to  the  outside,  so  that  the  water  is  wholly  and 
instantaneously  converted  into  steam  on  coming  into  con- 
tact with  the  heated  surface.  This  applies  to  all  the 
boilers  which  make  steam  by  flashing  the  water  into 
steam,  whatever  may  be  the  actual  design  of  the  boiler. 
This  method  was  first  suggested  by  John  Payne  in  his 
patent  of  1736  (No.  555)  and  paper  to  the  Royal  Society 
in  1747,  and  has  been  subsequently  tried  with  a  variety 
of  forms  of  boiler. 

3.  Mechanical  means  for  stirring  or  agitating  the  water,  pro- 

posed by  Sutton  Thomas  Wood  in  1784  (No.  1447),  "  to 
expose  a  greater  surface  of  the  heated  liquor  to  the  rarer 
medium  ;  and  by  opening  the  pores  of  the  water  to  cause 
the  weaker  steam  to  be  freed  from  that  weight  or  pres- 
sure that  before  confined  it,  and  enable  it  to  rise  and  mix 
itself  with  the  steam  above  the  surface  of  the  liquor  and 
thereby  increase  the  quantity." 

4.  Heating  surfaces  so  disposed  that   the   water,  instead  of 

being  in  a  compact  mass,  is  broken  up  into  thin  sheets,  so 
that  comparatively  small  quantities  are  acted  upon  by  the 
heat.  There  is  no  doubt  that  this  is  a  main  principle  of 
all  sectional  and  water- tube  boilers  ;  but  although  Wm. 
Blakey,  in  1766-1774  (No.  848),  and  James  Rumsey  in 
1788  (No.  1673)  had  introduced  two  forms  of  these,  it  is 
probable  they  had  in  view  merely  the  question  of  steam 
pressure  and  not  that  of  rapid  steam  generation.  In  that 
case  the  merit  of  perceiving  the  effect  of  sub-division  on 
steam  generation  would  rest  with  Matthew  Pitts,  who  in 
1793  (No.  1943)  announced  that,  though  "  the  received 
opinion  "  at  that  time  was  that  "  to  obtain  steam  a  com- 
pact body  of  water  was  required,"  and  u  where  a  great 
body  of  steam  is  wanted  a  great  body  of  boiling  water  is 
necessary,"  yet  he  had  ''found  from  experience  that  a 
large  quantity  of  steam  can  be  obtained  by  having  in 
use  a  small  quantity  of  water  disposed  so  as  to  cover  a 
large  surface  ;  and  the  quantity  of  the  steam  is  in  pro- 
portion to  the  extent  of  surface  and  strength  of  heat." 

The  value  of  sub-division  in  view  of  safety  from 
explosion  seems  first  to  have  been  set  forth  by  Aaron 
Manby  in  his  patent  of  1821  (No.  4558). 


THE  MODERN  STEAM  BOILER.  357 

5.  Revolving  Boilers. — These  apparently  aim  at  the  same  result 

as  do  the  arrangements  in  No.  3,  although  reversing  the 
order  of  procedure.  The  result  really  aimed  at  in  such 
devices  we  now  understand  to  be  increasing  the  efficiency 
of  the  heating  surface.  "  The  pores  of  the  water  "  were 
the  point  of  attack  in  olden  time,  but  now  it  is  the  trans- 
mission of  heat  to  and  through  the  boiler  surfaces  to  the 
water.  It  is  not  unlikely  that  the  idea  of  revolving 
boilers  may  have  been  suggested  by  such  engines  as 
Amonton's  fire-wheel  (of  1699),  described  and  illustrated 
in  Stuart's  "  Descriptive  History  of  the  Steam  Engine," 
or  by  some  other  form  of  the  rotary  engine,  the  idea  of 
which  was  popular  in  very  early  days. 

6.  Another  method    of  generating   steam,    which   had    some 

promise  of  success  from  more  than  one  point  of  view, 
was  suggested  as  early  as  1821  by  Aaron  Manby  in  his 
patent  No.  4558.  This  consisted  in  heating  a  compara- 
tively small  quantity  of  oil,  or  some  other  liquid  capable 
of  being  highly  heated  without  undergoing  decomposi- 
tion, and  causing  this  heated  substance  to  circulate 
through  tubes  or  passages  which  were  in  contact  with 
water.  This  plan  was  revived  as  lately  as  1876  (No. 
4235)  in  Barren's  boiler,1  but  the  temperatures  reached 
by  the  modern  use  of  high  pressures  practically  remove 
it  from  the  list  of  methods  of  working  now  available. 
In  a  modification  of  this  method,  applicable  to  boilers 
in  which  small  quantities  of  water  are  successively 
Hashed  into  steam,  a  fusible  alloy  was  employed  as 
the  medium  for  transmitting  the  heat  to  the  boiler 
surfaces. 

[See  also  J.  C.  Gamble  (No.  5327  of  1826)  and  Beale 
and  Porter  (No.  5609  of  1828)]. 

Jacob  Perkins'  method  might  be  considered  as  a 
distinct  system,  although  it  was  allied  in  a  certain  degree 
to  that  of  the  flash  boilers. 

Sectional  Steam  Boilers. — In  tracing  the  history  of   the  intro- 
duction of  sectional  or  water-tube  boilers,  some  writers  have 


1  See  Flannery  on  "The  Construction  of  Steam  Boilers  for  High  Pressures. 
Min.  Proc.  Inst.  C.E.,  Vol.  liv.,  p.  123. 


358 


THE  PRACTICAL  PHYSICS  OF 


gone  for  a  starting-point  to  Hero's  "Spiritalia  sen  Pneumatica,"1 
on  account  of  its  containing  two  designs  of  automatic  apparatus 
(composed  partly  of  vertical  tubes)  in  which  a  small  quantity  of 
steam  when  formed  was  used  to  blow  up  a  hre  placed  on  a 
grate  on  the  top  of  the  apparatus.  These  were  not,  properly 
speaking,  boilers — if  for  no  other  reason,  because  the  steam 
could  perform  no  useful  work  outside  of  the  apparatus  itself — 
but  were  merely  two  forms  of  the  philosophical  toys  or  wonder- 
working mechanisms  which  were  proposed  or  used  to  impress 
the  superstitious  fancy  of  an  ignorant  people.  Small  differences 
in  the  temperature  and  pressure  of  air  and  water  were  the  only 
forces  employed  in  them,  but  these  were  used  to  produce  often 
mysterious-looking  results. 

Apparently  the  earliest  design  of  a  sectional  or  water-tube 
boiler  on  record  is  that  of  Win.  Blakey,  who 
patented  in  1766  (No.  848)  some  improve- 
ments on  Savery's  engine.  A  high-pressure 
boiler  is  referred  to  in  his  patent,  but  accord- 
ing to  Stuart2  the  boiler  shown  in  Fig.  145 
was  not  invented  by  him  until  1774. 

The  boiler  as  thus  illustrated  consisted  of 
water  tubes  horizontally  placed  over  the  rire 
but  inclined  at  a  slight  angle  alternately  to 
right  and  left,  and  connected  at  their  ends 
by  bent  pipes,  so  as  to  provide,  with  these 
end  connections,  a  constantly  ascending  path  KK;.  145. 

for  the  steam  as  generated.     The  tubes  were 
thus  coupled  together  in  series,  and  formed   a  serpentine  coil  or 
flattened  spiral,  precisely  as  do   later    boilers,   notably  that    of 
Belleville,  of  which    Blakey's    may  be    taken   as    illustrating  a 
single  "  element  "  in  a  simple  form. 

A  water-tube  boiler  of  different  design  appears  to  have  been 
introduced  by  Fitch  and  Voight  into  a  small  steamboat  in 
America  in  1787.  This  design  is  represented  in  Fig.  146,  and 
the  boiler  consisted  of  an  iron  tube  coiled  backwards  and 
forwards  in  the  combustion  space  of  a  furnace  formed  of  brick- 

1  Published  in  the  Collected  Works  of  the  Ancient  Mathematicians.     Paris  : 
1693.   Also  Translated  into  English  by  Professor  Greenwood.    London  :.  1851 . 

2  Stuart's  Descriptive  History  of  the  Steam  Engine.     London  :  1824.    The 
Steam  Engine,  by  D.  K.  Clark,  Vol.  ii. 


THE  MODERN  STEAM  BOILER. 


359 


KIG.    146. 


work.  Consequently  this  was,  strictly  speaking,  a  coil  boiler, 
and  the  first  of  its  kind,  although,  in  a  general  way,  all  water- 
tube  boilers  in  which  the  steam  must  traverse  more  than  one 
tube  before  escaping  from  the  water  partake  of  the  nature  of 
coils.  James  Rumsey  claimed  that  he  was  the  inventor  of  this 

boiler,  and  had  a  public  controversy 
with  Fitch,  which  it  is  stated  l  was 
not  altogether  favourable  to  Rumsey. 
It  is  admitted,  however,  that  Rumsey 
began  experiments,  having  in  view 
the  application  of  steam  to  naviga- 
tion, in  1774,  and  in  1786  (according 
to  Professor  Thurston)  "  he  suc- 
ceeded in  driving  a  boat  at  the  rate 
of  four  miles  an  hour  against  the 
current  of  the  Potomac  at  Shepherds- 
town,  West  Virginia,  in  presence  of 
General  Washington."  This  boat 
was  propelled  by  means  of  a  water- 
jet,  but  we  are  not  informed  as  to  the  exact  design  of  boiler 
which  was  employed  in  it.  Rumsey  took  out  a  patent  in 
Britain  in  1788  (No.  1673),  in  which  he  described  more  than  one 
form  of  boiler,  the  designjintroduced  by  Fitch  and  Voight  being 
one  of  these,  whilst  there 
is  no  record  of  a  British 
patent  having  been  ob- 
tained by  these  latter. 

The  boiler  patented  in 
France  in  1793  by  Bar- 
low, and  introduced  into 
a  steamboat  there  some 
years  later  by  Robert 
Fulton,  a  celebrated  FIG.  147. 

American  engineer,  must 

also  rank  as  one  of  the  early  examples  of  water-tube  boiler 
design.  It  is  represented  in  Fig.  147,  and  the  illustration  shows 
it  to  have  been  constructed  of  iron  tubes  stretching  horizontally 
across  the  fires  and  having  their  ends  opening  into  flat  rectangular 

1  A    History   of  the    Growth  of  the    Steam    Engine,   by    Professor   R.    H. 
Thurston.     Vol.  xxiv.  of  the  International  Scientific  Series. 


360  THE  PRACTICAL  PHYSICS  OF 

boxes  or  chambers,  each  common  to  all  the  tubes,  and  forming 
a  side  of  the  boiler.  The  use  of  a  flat  chamber  of  such  area 
is  a  defect  noticeable  in  the  design  of  this  and  one  or  two  early 
boilers  of  the  same  class,  but  in  later  forms  it  disappears, 
as  "  headers "  of  comparatively  small  section  are  introduced. 
Barlow's  boiler1  is  said  to  be  preserved  at  the  Conservatoire 
des  Arts  et  Metiers  in  Paris,  but  there  is  no  record  of  its  design 
having  been  introduced  into  Britain  in  his  name.  One  of 
Rumsey's  designs  in  patent  No.  1673  of  1788,  seems  from  the 
description  to  resemble  Barlow's  plan. 

Tescheinacher's  Boiler, — The  patent  of  J.  R.  Teschemacher  (No. 
1808  of  1791)  contains  the  idea  of  a  him  system  of  evaporation 
applied  to  boilers.  His  boiler  was  in  form,  a  Hat  rectangular 
pipe,  placed  vertically,  and  containing  a  series  of  inclined  planes 
like  hollow  shelves,  on  which  the  \vater  was  made  to  flow  down- 
wards in  a  zig-zag  direction  from  one  hot  shelf  to  another.  The 
rectangular  pipe  wras  heated  externally  throughout  its  entire 
length  if  necessary,  and  communicated  with  a  vertical  steam- 
pipe  connected  \vith  the  various  inclined  cavities,  so  that  the 
steam  could  escape  as  it  was  formed. 

Whatever  the  defects  of  the  apparatus,  the  idea  of  exposing 
the  water  in  a  thin  layer  to  the  action  of  heat  was  original  and 
good.  It  has  not  often  been  applied  to  boilers,  but,  especially 
in  later  years,  has  become  of  importance  in  other  evaporating 
plant,  the  most  modern  forms  being  those  of  Yaryan  and 
Foster. 

Flash  Boilers. — The  system  first  suggested  by  Payne  found  in 
early  days  many  followers.  The  flashing  of  small  quantities  of 
water  into  steam  by  sudden  contact  with  very  hot  metal  surfaces 
was,  in  fact,  as  has  been  remarked  elsewhere,  a  favourite  idea 
with  early  inventors.  John  Payne's  patent  (No.  555  of  1736) 
did  not  describe  his  boiler,  but  later  he  gave  a  description  of  it 
in  a  paper  to  the  Royal  Society  of  London.2  It  appears  from 
that  account  that  his  boiler  wras  shaped  like  a  balloon,  the  middle 
portion  being  exposed  to  the  flame  and  hot  gases  from  a  furnace. 
Inside,  a  small  revolving  wheel,  like  a  Barker's  wheel,  threw  the 
water  in  spray  from  its  circumference  upon  the  highly  heated 

1  See   also    "  Des   Machines   a   Vapeur,"    by   A.    Morin  and    H.    Tresca. 
Hachette  and  Co.     Paris  :  1863.     Vol.  i.,  p.  253. 

2  See  Phil.  Trans.,  1747,  p.  828. 


THE  MODERN  STEAM  BOILER.  361 

surfaces,  on  coming  into  contact  with  which  it  was  at  once 
converted  into  steam.  Any  unevaporatecl  water  fell  to  the 
bottom  of  the  vessel  and  was  removed  by  a  pump.  Subsequent 
inventors  introduced  variety  in  the  details,  whilst  adhering  to 
the  main  system. 

Matthew  Pitts  and  Thos.  Strode  (No.  1867  of  .1792)  used  an 
"  ovoidal  "  vessel  or  chamber  having  a  tube  or  pipe  for  water 
inserted  at  the  top.  A  small  stream  of  water  falling  from  a 
height  through  this  pipe  splashed  into  spray  which  fell  on  the 
heated  surfaces. 

John  Dale  (No.  1950  of  1793),  on  the  contrary,  used  a  force 
pump  to  project  a  number  of  small  jets  of  water,  hot  from  a 
condenser,  against  the  upper  portion  of  a  boiler  surface  kept  at 
nearly  a  red  heat. 

Richard  Willcox  (No.  2493  of  1801)  did  not  describe  any 
special  form  of  apparatus,  but  seemed  to  appreciate  the  fact  that 
it  was  possible  to  have  the  metallic  plate  heated  to  such  a  point 
that  the  water  might  be  chemically  dissociated. 

John  Seaward  (No.  4356  of  1819)  proposed  to  use  a  flattened 
coil  of  tubes  set  in  a  furnace,  the  first  two  horizontal  lengths 
forming  the  roof  of  the  furnace  and  the  others  being  in  the  fine 
space  beyond.  The  water  was  to  be  heated  in  a  casing  or  jacket 
surrounding  the  vertical  flue,  and  injected  by  a  force  pump  into 
the  first  tube  of  the  series  placed  directly  over  the  fireplace.  On 
entering,  the  water  was  to  strike  against  the  apex  of  a  conical 
pkig  so  as  to  be  finely  sprayed  against  the  sides  of  the  tube. 

Sir  Wm.  Congreve  (No.  4593  of  1821)  proposed  injecting 
small  quantities  of  boiling  water  from  time  to  time  into  a  small 
inverted  receiver  placed  in  a  melted  alloy  melting  at  about 
300°  F.,  or  fusible  metal  melting  at  200°  F.  By  this  arrange- 
ment he  imagined  that  a  boiler  could  be  dispensed  with.  Alter- 
nately the  water  was  to  be  injected  on  the  heated  alloy  in  a 
vessel  or  chamber.  This  patent  has  a  better  claim  to  notice  in 
the  fact  that  it  contains  one  of  the  first  suggestions  for  super- 
heating steam  on  its  progress  from  the  boiler  to  the  cylinder. 
The  true  value  of  superheating  was  of  course  not  yet  known. 

John  Theodore  Paul  (No.  4950  of  1824)  formed  a  boiler  of  a 
continuous  length  of  copper  pipe  coiled  in  the  form  of  two  con- 
centric cylinders  or  spirals  slightly  conical,  the  annular  space 
between  the  two  being  occupied  by  the  fuel  which  was  to  be 


362  THE  PRACTICAL  PHYSICS  OF 

fed  into  it  from  a  pipe  or  shoot  above.  The  patent  set  forth 
that  for  a  two  horse-power  engine,  with  a  pressure  of  150  Ibs. 
per  square  inch,  the  copper  pipe  should  be  150  feet  long,  three- 
sixteenths  of  an  inch  internal  diameter,  and  one-sixteenth  in 
thickness.  This  might  be  supposed  to  be  an  ordinary  coil 
boiler  but  for  the  statement  in  the  patent  that  the  length  of  pipe 
should  be  sufficient  that,  when  heated  in  its  whole  length 
below  redness,  the  water  which  was  forced  into  it  at  one  end 
should  issue  from  the  other  end  as  steam  of  the  required  pres- 
sure. The  water  was  to  enter  at  the  top  of  the  outside  coil, 
descend  it,  and  then  ascend-  the  inner  one.  There  was  thus  no 
circulation,  in  the  ordinary  sense,  in  this  boiler,  but  the  water, 
gradually  wrarmed,  was  to  be  flashed  into  steam  as  soon  as  it 
reached  a  certain  point. 

John  McCurdy  (No.  4974  of  1824),  a  month  later,  proposed  a 
boiler  formed  of  cast  iron  tubular  chambers,  6  to  12  feet  in  length 
and  from  5  to  10  inches  in  the  bore,  having  a  small  perforated  tube 
or  injection  barrel  extending  through  the  whole  length  of  each. 
By  means  of  these  perforated  tubes  the  water,  when  forced  in  by 
a  pump,  was  sprayed  radially  throughout  the  whole  length  of 
the  chambers  and  flashed  into  steam  from  their  hot  surfaces. 

Wm.  Oilman  and  J.  W.  Sowerby  (No.  5150  of  1825)  proposed 
to  spread  the  water  in  a  thin  iilm  over  the  inner  surface  of 
cylindrical  boilers  by  means  of  the  centrifugal  action  of  agitators 
inside,  and  J.  C.  C.  Raddatz  (No.  5163  of  1825)  proposed 
vertical  metallic  tubes,  closed  at  the  bottom  end  and  coupled 
to  a  common  chamber  above,  to  be  wholly  immersed  in  a  bath 
of  fluid  tin  and  lead  alloy.  A  small  jet  of  water,  introduced  into 
the  top  of  each  tube  from  a  common  supply  pipe  led  through 
the  horizontal  steam  chamber,  instantly  formed  steam  by  contact 
with  the  heated  tube. 

These,  with  the  boilers  proposed  by  M.  S.  Boutigny  (see  No. 
786  of  1855)  and  M.  F.  Isoard  (No.  1637  of  1855),  are  amongst 
the  most  important  of  the  earlier  suggestions  for  that  method  of 
working.  In  more  recent  years,  this  system  has  been  more 
identified  with  a  tubulous  form  of  boiler,  or  with  capillary 
passages,  as  in  the  earlier  boilers  of  Herreshoff  and  Belleville, 
and  in  the  boilers  of  Serpollet  in  France,  De  Laval  in  Sweden, 
and  Simpson  and  Bodman  in  England. 

Jacob  Perkins*  System. — Although  it  was  to  some  extent  allied 


THE  MODERN  STEAM  BOILER.  363 

to  the  method  of  making  steam  by  flashing,  yet  the  system  pro- 
posed by  Jacob  Perkins  (in  No.  4732  of  1822,  and  No.  5477  of 
1827)  possessed  features  which  entitle  it  to  be  regarded  as  an 
entirely  original  one.  Perkins'  idea  was  to  heat  water,  in  a 
suitable  vessel,  to  400°  or  500°  F.,  the  vessel  being  .quite  full  of 
water.  Then,  by  forcing  an  additional  small  quantity  of  water 
into  the  vessel  by  a  pump,  a  corresponding  quantity  of  the 
superheated  water  would  escape  by  means  of  a  valve  into  a 
steampipe,  where  it  would  instantly  flash  into  steam.  He  first 
proposed  a  copper  cylindrical  vessel  of  three  inches  thickness  for 
this  process,  and  afterwards  described  a  boiler  composed  of 
small  horizontal  tubes  set  like  retorts  in  a  furnace,  similar  hori- 
zontal pipes  being  provided  for  the  steam  as  formed.  Apart 
from  the  fact  that  in  his  later  patent  he  proposed  to  pass  the 
steam  when  formed  through  water  which  was  not  externally 
heated,  and  would  thus  lose  heat  uselessly,  the  process  of  gene- 
rating steam  in  that  way  is  not  likely  to  be  economical  and  is  not 
free  from  objections  on  the  score  of  practicability. 

Practically  the  same  system  was  repatented  by  Samuel  Roberts 
on  nth  April,  1861  (No.  898). 

U'oolf's  Boiler. — Although  Richard  Shannon  (No.  2212  of  1798) 
proposed  an  arrangement  of  coppers  for  evaporating,  which  was 
also  suitable  for  the  construction  of  boilers  and  suggests  the  form 
of  Woolf's  boiler,  and  James  Sharpies  (No.   2576  of  1802)  pro- 
posed a  sectional  boiler  formed 
like    a   wheel,   yet   the  boiler 
patented  by  Arthur  Woolf  (No. 
2726    of    1803)    was    the    first 
practicable    water-tube    boiler 
after  Blakey's   and  Rumsey's. 
Woolf's  boiler,   Fig.  148,   was 
composed  of  horizontal  water- 
i --HI.  i4«-  tubes,  placed  over  a  lire  parallel 

to    one    another    and   a  small 

distance  apart.  When  nine  tubes  were  employed  the  fireplace  was 
formed  under  the  first  four  tubes,  then  the  flame  and  hot  gases 
were  carried  along  under  the  fifth,  above  the  sixth,  round  and 
under  the  seventh,  round  and  above  the  eighth,  round  and  below 
the  ninth,  then  back  by  a  zig-zag  flue  in  the  opposite  order  to  the 
front  of  the  boiler  and  then  to  a  chimney  placed  above.  Each 


364  THE  PRACTICAL  PHYSICS  OF 

horizontal  tube  was  connected  by  a  short  vertical  tube  to  a  large 
cylindrical  vessel  which  was  placed  transversely  across  the  centre 
of  the  tubes,  and  the  course  of  the  hot  gases  was  arranged  to 
miss  these  vertical  pipe  connections.  The  water  level  stood 
about  half  way  up  in  the  diameter  of  the  upper  chamber,  the 
upper  half  of  that  vessel  forming  the  steam  space. 

Cast  Iron  Boilers. — Woolf's  boiler  was  constructed  of  cast  iron, 
but  this  material,  although  much  used  for  boilers  in  early  days, 
could  not  attain  an  extended  use  in  presence  of  wrought  iron  or 
steel  when  they  became  available.  It  was,  howrever,  proposed 
for  the  sectional  boilers  invented  by  J.  McCurdy  in  1824  (No. 
4974),  which  was  a  flash  boiler  composed  of  tubular  chambers 
heated  on  the  outside,  with  concentric  perforated  tubes  for 
spraying  the  water  within  ;  of  Henrik  Zander  in  1839  (No. 

8  III.),  which  was  a  cellular 
form  of  boiler  ;  in  the  case  of 
the  first  Babcock  and  Wilcox 
boiler  ;  and  in  the  later  water- 
tube  or  sectional  boilers  of 
Miller,  Harrison,  Allen,  and 
the  Exeter  boiler. 

Stevens'    Boiler. — The    boiler 
made  by  John   C.  Stevens,  of 
F:G  New  York,  in   1804,  may  also, 

according  to  the  late  Mr.  Zerah 

Colburn,1  have  been  constructed  of  cast  iron,  but  the  particulars 
given  by  Professor  Thurston 2  would  rather  lead  to  the  conclu- 
sion that  it  was  formed  of  copper  tubes  cast  in  brass  tube  plates, 
one  end  of  the  tubes  being  plugged  by  caps  t>f  cast  iron  or 
brass. 

Stevens'  boiler  is  shown  in  Fig.  149.  It  contained  100  tubes 
2  inches  in  diameter  and  18  inches  long,  each  fastened  at  one 
end  to  a  central  water  chamber,  the  upper  part  of  which  formed 
a  steam  drum,  and  plugged  at  the  other  end,  a  bolt  passing 
through  each  cap  and  tieing  it  to  the  tubeplate. 

Stevens'  British  patent  was  taken  out  in  1805  (No.  2855),  but 
does  not  describe  the  boiler  illustrated. 

1  Proc.  Inst.  Mech.  Engineers,  1864,  p.  72. 

2  Hist,  of  the  Steam  Engine,  p,  266.      Trans,  of  the  Inst.  E,  and  St  in  Scot- 
land, Vol.  41,  p.  62. 


THE  MODERN  STEAM  BOILER. 


365 


Miller's  Boiler. — Miller's  boiler  was  undoubtedly  a  cast  iron 
boiler.  It  was  designed  by  Mr.  Joseph  A.  Miller,  of  New  York, 
and  was  introduced  into  Britain  in  1868,  having  been  described 
and  illustrated  in  Engineering  of  4th  December  and  The  Engineer 
of  25th  December  of  that  year.  An  account  of  it  was  presented 
to  the  Institute  of  Mechanical  Engineers  in  1871  by  Mr.  John 
Laybourne  (see  Proceedings  1871,  p.  263).  Its  form  is  shown  in 


THE    AMERICAN    SAFETY    BOILER. 


Sc.ilt    %'  I,    ,.n,/i»it. 


FIG.      150. 


Figs.  150  and  151.  It  was  constructed  of  a  number  of  units 
in  the  form  of  vertical  conical  tubes  connected  by  transverse 
horizontal  tubes  at  the  bottom  and  near  the  top.  The  fireplace 
was  formed  by  special  units  in  the  shape  of  a  semicircular  arch. 
Circulation  of  the  water  was  ensured  by  the  insertion  of  mid- 
feathers  in  the  furnace  units  and  internal  "  Perkins  "  or  "  Field  " 


tubes    in    the    rear    units.       Some    dimensions    and    results   of 
work  with  this  boiler  will  be  found  in  the  papers  quoted  above, 


366 


THE  PRACTICAL  PHYSICS  OF 


FIG.  D 


FIG.  C. 


FIG.  152, 


THE  MODERN  STEAM  BOILER. 


367 


and  in  "The  Steam  Engine,"  by  the  late  D.  K.  Clark  (Vol.  ii., 
p.  787). 


A'-  -v.v 


KIG.    153. 


Harrison's  Boiler. — The  boiler  designed  by  Mr.  Joseph  Har- 
rison, of  Philadelphia,  U.S.A.,  is  shown  in  Figs.  152,  153,  and  154. 


368  THE  PRACTICAL  PHYSICS  OF 

It  was  formed  of  hollow  cast  iron  spheres  connected  by  hollow 

Tnvu verse.    Sischoit,  Longib+dijial    Se^Uvn 

Detail  ol  one    Unit" 
A    Boiler 


FIG.    154. 


necks,  each  unit  casting  consisting  of  four  spheres  8  inches  external 
diameter,  |  inch  thick,  connected  by  necks  with  3^  inches  opening, 


THE  MODERN  STEAM  BOILER. 


369 


the  various  units  being  secured  together  by  internal  bolts  of  ij 
inch  diameter.  As  described  to  the  Institute  of  Mechanical 
Engineers  by  Mr.  Zerah  Colburn  in  1864  (Proceedings  1864, 
p.  61)  the  boiler  was  set  at  an  angle  over  the  lire,  but  a  later 
form  in  which  the  spheres  are  arranged  vertically  is  known 
as  the  Wharton-Harrison_Jboiler  and  is  illustrated  in  Fig.  155. 
Harrison's  British  patents  are  1859  (No.  1970)  and  1862  (No. 


FIG.    155. 


1340).  Some  results  of  trials  of  this  boiler  in  competition  with 
other  boilers  at  the  International  Exhibition  at  Philadelphia  in 
1876  will  be  found  in  Chapter  IX.,  and  in  "  The  Steam  Engine," 
by  D.  K.  Clark  (Vol.  i.,  pp.  253-263). 

Allen  Boiler. — The  Allen  boiler  is  also  of  American  origin,  and 
was  composed  of  horizontal  cast  iron  chambers  or  cylinders 
from  which  wrought  iron  tubes  3^  inches  diameter,  closed  at 
the  bottom  ends  by  screwed  caps,  depended  at  a  slight  angle. 


370 


THE  PRACTICAL  PHYSICS  OF 


It  is  represented  in  Fig.  156.  The  hanging  tubes  over  the  fire  are 
made  shorter  than  those  in  rear  of  the  furnace  in  order  to  form 
a  combustion  space.  As  these  tubes  were  not  furnished  with 
internal  tubes  for  circulation,  they  were  hung  at  an  angle  towards 
the  back  of  the  furnace  in  order  to  favour  circulation  and  sepa- 
ration of  the  steam  from  the  water.  Particulars  of  the  per- 
formance of  this  boiler  in  the  trials  at  the  American  Institute 
Exhibition  will  be  found  in  Chapter  IX. 

The  Exeter  Boiler,  Fig.  157,  consists  of  rectangular  hollow 
slabs  of  cast  iron,  placed  in  rows  across  the  boiler  setting,  and 
forming  a  series  of  vertical  leaves  or  chambers  pierced  with 
passages  for  the  hot  gases.  The  leaves  are  connected  by  small 
branch  pipes  passing  through  the  brickwork  to  a  steampipe 


FIG.    156. 

above  and  a  feedpipe  below.  The  steam  pipes  connect  with  a 
steam  drum  placed  across  the  centre  of  the  boiler  above  the 
brickwork.  The  water  level  stands  at  about  two-thirds  of  the 
height  of  the  leaves.  This  is  an  American  boiler  which  was 
tested  with  others  at  the  International  Exhibition,  Philadelphia, 
in  1876.  It  does  not  seem  to  have  been  widely  introduced. 

Horizontal  Tube  Boilers. — The  design  which  employs  horizon- 
tally placed  water  tubes — either  horizontal  or  slightly  inclined 
tubes — is,  as  we  have  seen,  the  earliest  which  was  used  in  the 
construction  of  water-tube  boilers,  and  it  remains  in  use  till  the 
present  day.  The  modifications  of  this  design  are  chiefly  con- 
cerned with  the  methods  by  which  the  ends  of  the  tubes  are 
connected,  and  these  methods  broadly  divide  these  boilers  into 
two  groups — viz.,  those  in  which  the  tubes  in  a  vertical  row  are 


THE  MODERN  STEAM  BOILER.  371 

connected  "  in  series,"  so  that  the  water  and  steam  must  traverse 
each  tube  in  the  row  successively,  and  those  which  have  the 
tubes  coupled  "  in  parallel,"  where  the  tubes  are  supplied  with 
water  from  a  common  water  chamber,  and  the  steam  from  each 
tube  can  escape  directly  to  the  steam  chamber  without  traversing 
more  than  a  single  tube.  The  former  method  is  illustrated  in 
the  boilers  of  Blakey,  Julius  Griffith,  1821  (No.  4630),  Moses 


Kid.    157. 

Poole,  1829  (No.  5815),  Andrew  Smith,  1838  (No.  7916),  ].  F. 
Belleville,  1852  (No.  725),  1856  (No.  1606),  1860  (No.  155),  1865 
(No.  3269),  and  Martin  Benson,  1858  (No.  1903).  The  latter 
method  finds  illustration  in  the  boilers  of  Rumsey,  Barlow, 
Woolf,  and  Stevens  already  mentioned,  and  in  those  of  Julius 
Griffith  (a  later  design  than  that  of  his  patent  of  1821),  W.  H. 
James,  1832  (No.  6297),  Joel  Spiller,  1835  (No.  6897),  Earl  of 
Dundonald,  1835  (No.  6923),  G.  H.  Moreau,  1842  (No.  9562), 
which  was  a  boiler  similar  to  Woolf's  but  made  of  copper  tubes  ; 


372  THE  PRACTICAL  PHYSICS  OF 

Thos.  Lawes,  1851  (No.  13440),  who  formed  channels  for  the  hot 
gases  by  placing  his  tubes  close  together  ;  John  Brayshay,  1856 
(No.  1738)  ;  W.  G.  Ramsden,  1860  (No.  589)  ;  Babcock  and 
Wilcox,  and  later  boilers.  In  the  case  of  the  boilers  of  F. 
Macaroni,  1839  (No.  8229),  W.  E.  Newton,  1849  (No.  I27^3)> 
and  A.  W.  Williamson  and  Loftus  Perkins,  1859  (No.  2208),  the 
movement  of  the  steam  and  water  was  necessarily  confused,  in 
consequence  of  the  method  of  connecting  horizontal  with 
vertical  tubes  which  was  adopted.  In  some  other  instances  the 
horizontal,  or  horizontally  inclined,  tubes  were  closed  or  plugged 
at  one  end,  and  therefore  only  opened  into  boxes  or  headers  at 
one,  usually  the  front,  end.  This  finds  illustration  in  the  boilers 
of  Alban  (about  1843),  Kelly,  Lane,  Niclausse  and  Dtirr,  the  four 
latter  having  either  internal  tubes  or  diaphragms  for  circulation 
of  the  water  by  separating  the  currents  of  steam  and  water. 
Both  the  "  Barrow "  boiler  of  J.  and  F.  Howard  and  Root's 
boiler  have  a  modification  of  the  parallel  coupling  ;  whilst  a 
recent  one  of  F.  E.  Rainey  has  a  combination  of  both  series  and 
parallel  couplings  in  the  same  boiler,  the  series  connections  being 
of  course  short-circuited  by  this  means. 

A  boiler  constructed  of  horizontal  tubes  coupled  in  series  and 
forming  in  this  way  a  flattened  spiral  is  not  properly  a  coil 
boiler,  because,  not  only  is  the  horizontal  tube  the  unit  proper  of 
the  boiler,  but  also,  in  general,  the  bends  or  end  connections  are 
either  not  at  all,  or  only  slightly,  exposed  to  the  heat,  and  are  not 
used  as  part  of  the  heating  surface  for  steam  generation.  The  fact 
that  there  are  joints  to  preserve  at  these  parts  is  sufficient  reason 
why  they  should  be  treated  differently  from  the  body  of  the  tubes. 

Similarly  there  is  no  reason  why  the  boilers  of  Lane,  Niclausse, 
Kelly,  and  Diirr  should  be  considered  as  being  anything  but 
horizontal  tube  boilers,  any  more  than  should  the  boiler  of 
Alban.  The  mere  fact  that  they  have  provision  for  the  circula- 
tion of  the  water  in  the  horizontal  tubes  by  means  of  internal 
concentric  tubes,  which  Alban  had  not,  only  differentiates  them 
as  to  completeness  of  detail  and  not  as  to  the  general  form  or 
design. 

It  is  apparent  that  the  action  taking  place  in  boilers  of  any 
of  these  groups  is  substantially  the  same  as  that  which  goes  on 
in  the  others,  in  this  respect,  that  the  steam  which  is  generated 
in  any  of  the  horizontal  tubes  must  at  once  rise  to  the  upper 


THE  MODERN  STEAM  BOILER.  373 

surface  of  the  tube  along  which  it  will  proceed  to  the  end. 
This  is  shown  in  the  illustration  of  a  glass  model  of  such  a  boiler 
(Fig.  no).  Where  steam -is  being  generated  very  rapidly  a  con- 
siderable proportion  of  the  upper  surface  of  the  tubes  will  thus 
be  in  contact  only  with  steam  within,  and  although  that  portion 
may  be  shielded  from  the  radiant  heat  of  the  lire,  yet  it  is  ex- 
posed to  contact  with  flame  and  hot  gases  on  the  outside,  and 
is  therefore  liable  to  be  raised  to  a  higher  temperature  than  the 
.lower  half  of  the  tube  which  retains  water  in  contact  with  its 
surface.  This  tends  to  the  production  of  strains  in  the  indi- 
vidual tubes,  which  should  be  avoided.  In  the  group  with 
"  series  "  connections  this  result  is  necessarily  accentuated,  as 
each  tube  in  a  series  has  to  convey  not  only  the  steam  generated 
within  itself,  but  also  all  generated  in  the  tubes  immediately 
below  it  in  that  series.  In  result,  too,  this  causes  the  topmost 
row  or  rows  of  tubes  to  be  practically  denuded  of  water  ;  that 
which  they  contained  at  starting  having  been  forced  upwards 
into  the  steam-drum  by  the  rush  of  steam  from  below,  and  the 
same  cause  operates  in  preventing  any  of  that  water  draining 
back  into  these  tubes  from  the  steam  drum.  No  water,  or  only 
a  little  in  a  frothy  foam,  can  reach  these  tubes  from  below,  so 
that  in  such  cases  there  may  be  a  row  or  t\vo  of  tubes  which  are 
wholly  raised  to  a  higher  temperature  than  those  lower  down, 
and  this  will  introduce  further  strains  in  the  structure  of  the 
boiler. 

It  is  apparent  that  no  advantage  can  be  derived  from  causing 
the  steam  to  be  detained  in  contact  with  the  water,  but  that,  on 
the  contrary,  the  steam  once  formed  should  be  able  to  escape 
by  a  direct  route  straight  to  the  steam  chamber.  For  similar 
reasons,  as  soon  as  the  steam  and  the  water  carried  up  by  it 
have  separated,  the  water  should  be  returned  by  the  most  direct 
road  to  the  point  at  which  it  is  available  for  supply  to  the  heat- 
ing surfaces.  Even  with  vertical  water  tubes  a  rapid  generation 
of  steam  causes  the  projection  of  a  good  deal  of  water  into  the 
steam  chamber  along  with  the  steam,  and  there  is  nothing  in 
the  horizontal  tube  design  to  cause  that  action  to  be  less  in  its 
case. 

Boilers  of  this  design  have  the  further  disadvantage  that,  if 
placed  athwartships  in  a  steamer,  they  are  liable  to  have  their 
circulation  of  water  and  steam  interrupted  and  even  reversed 


374 


THE  PRACTICAL  PHYSICS  OF 


during  and  in  consequence  of  the  rolling  of  the  ship  in  a  sea- 
way. As  long,  however,  as  the  present  rate  of  steam  generation 
per  square  foot  of  surface  continues  to  be  the  best  result  aimed 
at,  it  is  probable  that  this  design  of  boiler  will  be  used,  and  will 
compare  more  or  less  favourably  with  other  designs,  worked 
under  the  same  conditions. 

Hancock's  Boiler. — Amongst  early  examples  of  this  form  of 
boiler  Mr.  C.  H.  Wingfield  advanced  the  one  shown  in  Fig.  158, 
which  he  ascribed  to  Walter  Hancock,  who  was  best  known  in 
connection  with  the  use  of  a  cellular  form  of  boiler  in  road 

vehicles.  Mr.  Wingfield  said l  that, 
"  in  connection  with  Hancock's  boiler, 
it  was  not  generally  known  that  he  at 
first  used  a  boiler  with  horizontal 
tubes  connected  at  their  ends,  Fig.  158. 
This  he  abandoned  for  his  boiler  of 
182.7,  consisting  of  flat  leaves,"  &c. 
Mr.  Wingfield,  however,  did  not  men- 
tion from  what  source  he  derived  his 
information,  and  the  boiler  illustrated 
was  not  patented  by  Hancock. 

Griffith's  Boiler.  —  Another  early 
boiler  made  on  this  plan  was  the  one 
employed  by  Mr.  Griffith  in  his  steam 
carriage2  built  by  Bramah.  This  is 
shown  in  Fig.  159.  Griffith's  patent 
of  1821  described  a  boiler  of  hori- 
zontal tubes  connected  at  the  ends  by 
semicircular  bends,  the  feed  water  being  caused  to  travel 
through  the  whole  in  series.  In  this  instance  of  experimental 
work,  however,  he  adopted  the  parallel  system  of  coupling  the 
tubes,  as  will  be  seen.  We  have  it  from  Sir  F.  Bramwell 3  that 
this  boiler  never  could  be  kept  tight,  so  that  the  steam  carriage 
did  not  succeed  ;  and  Mr.  A.  Gordon,  in  his  "  Historical  and 
Practical  Treatise  upon  Elemental  Locomotion  by  means  of 
Steam  Carriages  on  Common  Roads,"  records  a  similar  result. 

1  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scotland.     Vol.  xli.,  pp.  81-82. 
'2  Gordon's  Locomotion  on  Common  Roads,  p.  41. 

3  Reminiscences   of    Steam   Locomotion   on    Common   Roads.     Section   G, 
British  .Assoc.,  1894.     Engineer  17  Aug.,  1894,  P-  J52- 


FIG.   158. 


THE  MODERN  STEAM  BOILER. 


375 


Although  only  six  horizontal  tubes  and  two  vertical  boxes,  or 

headers,  are  shown  in  the  Fig.  159,  similar  rows  of  tubes  and 

headers  were  placed  behind  these,  so  that  there  were  114  tubes 

in  the  boiler.     Three  transverse  horizontal  steam  domes  were 

placed     above     as     shown. 

The    horizontal    tubes,    Mr. 

Gordon     remarks,     "  would 

not   always    contain    water, 

and   when    empty,    got    so 

heated  that  no  force  pump 

could  inject  the  water  ;  on 

this   account    the    invention 

was  dropped." 

Andrew  Sinit/i's  Boiler. — 
The  boiler  of  Andrew  Smith, 
mentioned  above,  possessed 
the  original  feature  that, 
whilst  the  rows  of  horizontal 
tubes  were  connected  in 
series,  their  diameter  was 
increased  as  the  rows  as- 
cended. This  showed  that 
he,  at  any  rate,  appreciated 
the  effect  of  that  mode  of 
connection  upon  the  steam 
and  water  circulation  in  the 
boiler. 

Alban's  Boiler.  —  About 
1843  Dr-  Ernst  Alban,  of 
Plan,  Mecklenburg,  intro- 
duced a  water-tube  boiler 
composed  of  horizontal 
tubes  slightly  inclined  up- 
wards towards  the  front 
end,  at  which  they  were 
screwed  to  the  backplate  of  a  rectangular  chamber.  Figs. 
1 60,  161  and  162  illustrate  this  boiler.  The  tubes  were  of 
copper  4  inches  in  diameter,  11()th  inch  thick,  and  from  4^  to 
6\  feet  in  length,  according  to  the  size  of  boiler  wanted. 
The  rows  were  disposed  so  as  to  break  joint  vertically,  the 


FIG.    159. 


376 


THE  PRACTICAL  PHYSICS  OF 


advantages  of  this  arrangement  in  view  of  the  circulation  of  the 
heated  gases  being  apparent.  (See  on  this  point  N.  J.  Suckling, 
"  On  Modern  Systems  of  Generating  Steam,"  Society  of  Engi- 
neers, 1874,  and  The  Engineer,  28th  February,  1873,  and  2Qth 
May,  1874  ;  and  James  Howden,  "  The  Comparative  Merits  of 
Cylindrical  and  Water-tube  Boilers  for  Ocean  Steamships," 
Trans.  Inst.  N.  A.,  1894.)  An  English  translation  of  Dr.  Alban's 
treatise  was  published1  in  1848,  and  his  boiler  was  described  by 
Mr.  Vaughan  Pendred  in  a  paper  on  "  Water-tube  Boilers  " 
(Transactions  of  the  Society  of  Engineers,  6th  May,  1867),  and 
by  Mr.  D.  K.  Clark  in  "The  Steam  Engine,"  &c.  (Vol.  ii., 
Pi  756).  The  back  ends  of  the  tubes  were  closed  by  a  screw 
cover  in  each,  which  could  be  removed  for  the  purpose  of 
cleaning  out  the  tube.  The  provision  made  for  circulation  of 


FIG.    1 60. 


FIG.  161 


FIG.    162. 


the  water  in  the  tubes  was  limited  to  certain  arrangements  in 
the  front  chamber.  At  the  end  of  each  tube  there  were  two 
oval  openings  in  the  backplate  of  the  chamber,  the  upper  one 
for  the  escape  of  steam  from  the  tube  and  the  lower  one  for 
admission  of  water  to  the  tube.  The  chamber  itself  was  con- 
nected to  two  cylindrical  horizontal  vessels  above,  placed  in  the 
same  direction  as  the  tubes,  and  the  connection  from  one  of 
these  \vas  carried  clown  to  the  bottom  of  the  front  chamber, 
whilst  the  other  had  access  directly  to  the  top  of  it.  The 
intention  of  this  was  to  convey  the  water  from  one  down  to  the 
lowest  point  in  the  tube  chamber,  from  which,  in  flowing 
upwards,  it  was  directed  across  the  rows  of  tubes  by  division 
plates,  and  these  also  served  to  direct  the  steam  clear  of  the 


1  The  High-Pressure  Steam  Engine,  by  Dr.  Ernst  Alban. 
the  German  by  Dr.  Wm.  Pole,  F.K.S.      1848. 


Translated  from 


THE  MODERN  STEAM  BOILER. 


377 


tubes  above,  so  that  it  collected  on  the  side  where  it  found  the 
opening  into  the  other  horizontal  vessel  above. 

Figures  of  proportions  of  this  boiler  and  of  results  of  working 
will  be  found  in  the  papers  quoted  above. 

Belleville's  Boilers. — The  first  British  patent  taken  out  by  Julien 
Francois  Belleville  was  dated  in  November,  1852  (No.  725).  It 
described  a  combination  of  horizontal  and  vertical  coiled  pipes, 
and,  as  made,  the  boiler  was  probably  not  unlike  the  one  illus- 
trated in  Bertin  and  Robertson's  "  Marine  Boilers"  (p.  224)  as 
having  been  tried  in  the  u  Biche," 
without  success. 

In  July,  1856  (No.  1606),  another 
arrangement  of  these  coiled  or 
serpentine  tubes  was  proposed. in 
which  only  horizontal  tubes  were 
employed.  In  both  of  these 
designs  the  water  was  first  heated 
in  the  portions  of  the  coils  or 
tubes  farthest  from  the  fire,  and 
after  circulating  in  them  was 
made  to  pass  through  those 
nearer  the  fire,  finally  finishing  in 
those  immediately  over  or  at  the 
side  of  the  furnace.  This  was 
practically  the  flashing  system, 
as  the  tubes  exposed  to  the  direct 
heat  of  the  fire  could  never  con- 
tain any  water,  although  they 
might  be  useful  in  superheating 
the  steam. 

Further  patents  in  1860  (No.  155),  1865  (No.  3269),  and  1866 
(No.  2976),  followed,  from  which  the  modern  form  of  the 
Belleville  boiler  has  been  developed. 

Patents  were  also  taken  out  in  1869,  1872,  1880  (No.  5447), 
1884  (No.  11851),  1889  (Nos.  14873  and  15356),  and  1892  (Nos. 
11615,  22250,  and  22251),  1895  (Nos.  1336  and  1729),  1896  (No. 
14868).  An  early  form  of  the  Belleville  boiler,  in  which  junc- 
tion boxes  were  used  only  at  the  front,  the  tubes  being  bent  at 
the  back  so  as  to  bring  both  ends  parallel  to  the  front,  one  being 
above  the  other,  is  illustrated  in  Mr.  Thornycroft's  paper  on 


378 


THE  PRACTICAL  PHYSICS  OF 


Water-tube  Steam  Boilers  in  Min.  Proc.   Inst.  C.  E.,  Vol.  xcix., 
Plate  L,  Figs.  3a. 

The  first  of  these  latter  patents  (1860)  describes  the  boiler 
illustrated  in  Fig.  163,  which  is  quite  a  coil  boiler,  but  did  not 
succeed  when  tried"  in  the  "  Argus  "  and  the  "  Sainte  Barbe  "  in 
1861.  This  form  bears  some  resemblance  to  the  earlier  arrange- 
ment of  parts  in  the  Du  Temple  boiler. 


FIG.    164. 

In  the  boilers  of  1866,  1869,  and  1872,  the  feed  inlet  enters 
directly  opposite  the  end  of  the  lowest  horizontal  tube  in  the 
front  box  or  header,  and  the  steam  separator  is  merely  a  tube  of 
small  diameter  surmounting  a  similar  tube  used  as  a  collector, 
small  branch  pipes  connecting  the  two.  In  the  later  boilers  the 
connecting  boxes  at  the  ends  are  placed  horizontally,  instead  of 
vertically  as  formerly,  a  feed  collector  and  arrangements  for 


THE  MODERN  STEAM  BOILER. 


379 


Front  elevation 


380 


THE  PRACTICAL  PHYSICS  OF 


Side  elevation. 


THE  MODERN  STEAM  BOILER.  381 

automatic  regulation  of  the  feed  are  added,  and  the  steam 
separator  is  a  vessel  of  cylindrical  form  with  internal  baffle 
plates.  The  latest  forms  have  in  addition  a  feed-heater  com- 
posed of  short  tubes,  arranged  like  the  steam  generating  tubes, 
placed  in  the  flue  space  above  the  generator. 

Fig.  164  shows  the  modern  form  without  feed-heater,  and 
Figs.  165  and  166  the  arrangement  finally  adopted  writh  feed- 
heater.  Detailed  descriptions  will  be  found  in  Berlin  and 
Robertson's  "  Marine  Boilers,"  Sennett  and  Gram's  "  Steam 
Engine,"  and  in  various  papers  in  the  Proc.  Inst.  C.  E.  and 
Trans.  Inst.  N.  A. 

The  Belleville  boilers  of  H.M.S.  "  Diadem  "  are  illustrated  in 
The  Mechanical  Engineer  of  9th  April,  1898. 


FIG.    167. 

Wilcox' s  Boiler. — The  boiler  shown  in  the  accompanying 
illustration  (Fig.  167)  is  said  by  Professor  Thurston  to  have  been 
invented  by  Stephen  Wilcox  in  America  in  1856,  and  thus  in 
a  certain  way  to  have  led  up  to  the  Babcock  and  Wilcox  boiler 
of  to-day,  although  there  were  some  intermediate  steps. 

Benson'' s  Boiler. — A  very  interesting  water-tube  boiler  in  this 
class  of  horizontal  or  horizontally  inclined  tube  boilers  was 
patented  by  Martin  Benson  in  1858  (No.  1903),  and  again  in 
1861  (No.  834).  The  small  horizontal  tubes  of  i  inch  or  ij 
inch  diameter  were  connected  by  semicircular  cast  iron  bends 
or  junction  pieces  at  the  ends,  and  were  arranged  in  series  in  a 
vertical  direction  to  form  a  number  of  flattened  spirals  placed 
side  by  side.  The  bends  were  placed  vertically  at  the  back  of 
the  boiler  and  horizontally  at  the  front  end  of  the  tubes,  so  that 


382  THE  PRACTICAL  PHYSICS  OF 

one  vertical  section  or  compartment  of  the  boiler  consisted  o 
two  horizontal  tubes  side  by  side  but  in  rows  zig-zagged  or 
"  staggered  "  in  an  upward  direction  (see  Figs.  168  and  169.  In 
describing  this  boiler  to  the  Institute  of  Mechanical  Engineers 
(Proceedings  1859,  P-  264'),  Mr.  J.  F.  Spencer  said  that  the 
uncertainty  of  what  may  be  termed  natural  circulation  had  led 


.?..../ 


FIG.   1 68. 

to  the  introduction  of  mechanical  circulation  as  a  distinctive 
feature  of  this  boiler,  and  that  ten  to  twenty  times  the  quantity 
of  water  required  for  steam  might  be  passed  through  the  boiler 
in  a  given  time. 

The  pump  for  mechanical  circulation  was  connected  writh  the 

1  See  also  Proc.  1861,  p.  30,  and  Plate  xxiii. 


THE  MODERN  STEAM   BOILER. 


383 


steam  receiver,  which  also  acted  as  a  separator  and  water 
chamber,  and  showed  the  water  level  of  the  boiler,  being 
placed  at  the  back  or  side  of  the  boiler  and  not  above  the 
tubes.  "  It  will  be  evident,"  said  Mr.  Spencer,  "  that  a  small 
amount  of  power  is  required  to  work  the  circulating  pump,  since 


DthuJ,  cf    TUJH.S      cnJaryc-d- 


FIG.    169. 

the  pressure  is  almost  equal  on  each  side  of  the  piston,  so  that, 
whether  this  pressure  be  100  or  500  Ibs.  per  square  inch,  only 
the  friction  of  the  water  has  to  be  overcome  in  effecting  the 
circulation.  A  boiler  of  100  nominal  horse-power  would  re- 
quire a  circulating  pump  of  only  7  inches  diameter  and  12 
inches  stroke,  making  50  revolutions  per  minute."  Supposing 


384 


THE  PRACTICAL  PHYSICS  OF 


that  10  cubic  feet  of  water  were  evaporated  per  hour,  about 
100  cubic  feet  would  be  passed  through  the  circulating  pipe  and 
the  tubes  by  the  circulating  pump.  In  addition  to  the  circu- 
lating pump,  an  ordinary  feed  pump  was  used  to  supply  the 
deficiency  of  water  caused  by  evaporation. 

Williamson  and  Perkins  Boiler. — In  September,  1859  (No. 
2208),  A.  W.  Williamson  and  Loftus  Perkins  patented  the  boiler 
composed  of  horizontal  water  tubes  united  by  short  vertical 
tubes,  which  was  afterwards  known  as  Perkins'  boiler.  This 
boiler  was  described  and  illustrated  in  the  Proceedings  of  the 


FIG.    170. 

Institute  of  Mechanical  Engineers  in  1861  (page  95  and  Plate 
xxiii.),  Fig.  170,  and  a  later  form  was  described  by  Mr.  Loftus 
Perkins  in  1877. *  (See  also  Perkins  and  Harris,  1880,  No.  168.) 
Fig.  171,  172  and  173  shows  the  later  form  as  arranged  for  a 
marine  boiler.  The  joints  connecting  the  horizontal  tubes  with 
the  short  vertical  tubes  were  all  screwed,  but  there  was  no 
proper  provision  made  in  this  boiler  for  the  circulation  of  the 
water.  In  fact,  Mr.  Perkins  used  to  claim  as  a  feature  of  the 
boiler  that  it  made  steam  by  "  foaming "  and  not  by  means 
of  circulation  as  properly  understood.  Some  of  the  fallacies 


Proc.  Inst.  Mech.  Eng.,  1877,  p.  117. 


THE  MODERN  STEAM  BOILER. 


385 


grouped  around  this  system  were  exposed  in  an  article  (by  the 
author  of  this  work)  which  appeared  in  Engineering  of  3oth 
March,  1877  (Vol.  23,  p.  251)  entitled  "  Amateur  Science  at  the 
Royal  United  Service  Institution."  Examples  of  Perkins' 
boilers  were  fitted  in  the  s.s.  "  Anthracite  "  and  in  the  s.  yacht 


FIG.    171. 


"  Wanderer,"  but  these  were  not  permanently  successful. 
Little,  however,  was  allowed  to  become  known  of  their  history 
after  preliminary  trials. 

Boilers   of  the   s.s.   "  Montana  "   and    "  Dakota" — There   is  a 
strong  family  resemblance  between  the  Perkins  boiler  and  the 


386 


THE  PRACTICAL  PHYSICS  OF 


boilers  fitted  in  1875  by  Messrs.  Palmer,  of  Jarrow-on-Tyne,  in 
the  steamships  "  Montana  "  and  "  Dakota."  In  the  latter  the 
diameters  of  horizontal  tubes  and  of  the  vertical  connecting 
tubes  or  necks  are  larger,  so  that  apparently  there  is  more 
freedom  of  circulation  possible,  but  this  was  neutralised  by 


mmimimmmimmm 


FIG.   172. 

inadequate  steam  and  feed  connections.  Moreover,  the  vertical 
necks  had  to  serve  for  both  the  ascent  of  the  steam  and  any 
water  carried  up  by  it,  and  the  descent  of  the  water  so  carried 
up.  Figs.  174  and  175  show  the  profile  of  these  boilers,  par- 
ticulars of  the  trials  of  which  were  given  by  Mr.  W.  Parker  (in 


THE  MODERN  STEAM   BOILER. 


387 


FIG.    173. 


FJG.    174. 


FIG.  175. 


O    2 


388 


THE  PRACTICAL  PHYSICS  OF 


Min.  Proc.  Inst.  C.  E.,  Vol.  xcix.,  p.  106)  and  by  Mr.  J.  Fortescue 
Flannery  in  Trans.  I.N.A.,  1876. 

Ramsdens  Boiler. — In  the  boiler  patented  by  Mr.  W.  G. 
Ramsden  in  1860  (No.  589)  horizontal  tubes  of  comparatively 
large  diameter  were  connected  at  their  ends  to  vertical  chambers, 


KIG.    I77. 


FIG.    178. 

semi-circular  in  cross-section.  This  boiler  is  represented  in 
Figs.  176,  177  and  178,  which  show  the  boilers  fitted  in  the 
steamships  "  Amalia  "  and  u  Palm."  Having  been  worked  with 
sea- water,  these  boilers  were  practically  destroyed  by  incrusta- 
tion after  about  four  vears'  work. 


THE  MODERN  STEAM  BOILER. 


389 


Babcock  and  Wilcox  Boilers. — The  original  Babcock  and 
Wilcox  boiler  was  constructed  of  cast  iron,  and  is  illustrated  in 
Professor  Thurston's  "  Manual  of 
Steam  Boilers/' from  which  Fig.  179 
has  been  taken.  It  was  introduced 
in  America,  and  was  subjected  to 
various  improvements  in  design, 
in  which  the  cast  iron  headers  and 
tubes  were  replaced  with  wrought 
iron.  British  patents  were  taken 
out  in  1880  (No.  2615),  1881  (No. 
5289),  1884  (No.  13041),  1885 
(Nos.i836,  3979, 4133, 4134, 10821), 
1886  (No.  5887),  1887  (Nos.  3059, 
8228,  11789,  11887),  and  in  1890,  1891,  &c. 

The    Babcock- Wilcox  marine   boiler   is  shown    in  a   patent 
taken  out  in  1896  (No.  24617). 


Various  details  were  also  patented  by  C.  A.  Knight  and  others 
connected  with  the  boiler.  After  considerable  success  in  land 
installations,  it  was  introduced  in  vessels  of  the  American  navy, 
and  a  modified  form  for  marine  use  was  fitted  in  the  s.s.  "  Nero  " 


39° 


THE  PRACTICAL  PHYSICS  OF 


and  some  other  merchant  vessels,  and  in  H.M.S.  "  Sheldrake,"  in 
this  country.  The  land  form  is  also  in  extensive  use  in  this  country. 
In  the  land  boiler  the  horizontally  inclined  tubes  incline 
downwards  from  front  to  back,  and  are  secured  at  each  end  to 
wrought  steel  headers  of  square  section  and  sinuous  form  verti- 
cally, so  that  the  tubes  are  "  staggered  "  to  baffle  the  gases  in 
their  movement  amongst  them.  A  cylindrical  steam  and  water 


FIG.    l8l. 

drum  runs  longitudinally  from  front  to  back  above  the  tubes, 
and  the  headers  are  each  separately  connected  to  it  at  either 
end  by  vertical  tubes  or  nipples.  A  mud  collector  is  connected 
to  the  lower  side  of  the  back  headers.  The  working  water  level 
being  at  about  the  middle  of  the  steam  and  water  drum,  the 
movement  of  the  water  in  circulation  is  always  in  the  same 
direction,  upwards  through  the  inclined  generating  tubes  and 


THE  MODERN  STEAM  BOILER.  391 

the  front  headers  and  downwards  through  the  back  headers. 
Figs.  180,  181  and  182  show  this  form  and  some  details. 

In  the  marine  form  each  of  the  inclined  tubes  is  replaced  by 
a  group  of  four  tubes   of    small  diameter,  and  there  are  two 


drums  above — the  larger  one  placed  across  the  boiler  at  the  top 
of  the  back  headers,  which  are  connected  to  it  by  short  direct 
nozzles.  In  this  drum  the  water  level  is  at  the  centre,  as  in  the 
land  boiler  drum,  but  there  is  a  smaller  drum  a  little  above  it, 


392 


THE  PRACTICAL  PHYSICS  OF 


and  alongside,  which  is  used  as  a  feed  purifying  chamber,  the 
feed  being  introduced  into  it.  In  the  boiler  of  the  s.s.  "  Nero  " 
the  upper  chamber  was  used  as  a  steam-chest,  and  there  were 


FIG.    183. 


vertical  water  tubes  set  round  the  boiler  to  form  a  casing,  but 
these  seem  to  have  been  removed  in  the  later  examples.  The 
front  headers  are  connected  to  the  steam  and  water  drum  by 
tubes  passing  horizontally  across  the  top  of  the  inclined  tubes. 


THE  MODERN  STEAM  BOILER. 


Special  fittings  with  metal  to  metal  joints  are  made  for  the 
hand  holes,  and  so  arranged  that,  should  a  holding  bolt  break, 
they  are  held  in  place  by  the  steam  pressure. 

Figs.  183  and  184  show  the  later  arrangement  of  this  boiler. 
An  illustration  of  the  "Nero's"  boiler  in  outline  will  be  found 
in  the  Engineer  of  2ist  July,  1893,  page  73,  Fig.  I. 


FIG.    184. 


Root  Boiler. — The  Root  boiler  was  introduced  in  America 
shortly  after  the  Babcock  and  Wilcox  boiler,  but  preceded  it  in 
this  country,  having  been  patented  in  1870  (No.  1675),  and,  after 
some  use  in  land  installations,  having  been  tried  in  the  steamer 
"  Birkenhead  "  in  1872. !  The  horizontally  inclined  tubes, 
usually  about  4^  inches  diameter,  are  sloped  downwards  towards 
the  back,  and  are  screwed  at  back  and  front  into  rectangular 
box  castings,  which  are  connected  vertically  by  hollow  castings 
bolted  on  and  forming  means  of  communication  from  tube  to 

1  See  Engineering,  2ist  April,  1876. 


394 


THE  PRACTICAL  PHYSICS  OF 


tube.  These  hollow  castings  are  so  placed  as  to  give  a  zig-zag 
course  of  ascent  for  the  steam  and  water.  Figs.  185  and  186 
show  the  arrangement  finally  adopted  as  the  most  satisfactory. 
A  later  arrangement,  introduced  by  Messrs.  Conrad  Knap  and  Co., 
having  bent  pipe  connections  between  the  various  box  castings 
instead  of  the  American  bracket-shaped  hollow  castings  afore- 
said, is  shown  in  Figs.  187,  188  and  189.  A  description  of  the 
boilers  fitted  in  the  "  Birkenhead  "  and  "  Malta  "  was  given  by 
Mr.  J.  Fortescue  Flannery  in  a  paper  "  On  Water-tube  Boilers  " 
in  Trans.  Inst.  N.A.,  1876  (Vol.  xvii.,  p.  259). 

This  boiler,  as  well  as  the  one  next  to  be  referred  to,  has  a 

modified  arrangement  of  the 
coupling  "  in  parallel,"  inas- 
much as  there  are  not 
headers  common  to  all  the 
tubes  at  either  end  of  these, 
but  a  number  of  small  pas- 
sages formed  by  box  castings 
or  the  like,  by  means  of 
which  the  steam  and  water 
are  passed  from  tube  to  tube, 
or  zig-zagged  upwards. 

Howard's  "Barrow"  Boiler. 
— The  horizontal  tube  boiler 
introduced  by  Messrs.  J.  and 
F.   Howard  in   1866,  which 
FIG.  185.  was    afterwards    called   the 

"  Barrow   sectional    boiler," 

was  described  in  one  form  by  Mr.  David  Joy  to  the  Iron  and  Steel 
Institute  in  1875  (see  Vol.  No.  i.,  1875,  p.  220,  and  Plates).  A 
later  form  is  shown  in  Fig.  190,  taken  from  D.  K.  Clark's  "  Steam 
Engine."  The  tubes  were  inclined  upwards  to  the  back  of  the 
boiler,  where  five  of  the  six  tubes  forming  one  vertical  group 
were  coupled  to  a  vertical  collecting  pipe.  At  the  front  the  feed- 
water  was  introduced  into  the  lowermost  tubes  from  a  square 
cast  iron  chamber  laid  horizontally  across  the  front  of  the 
boiler,  and  the  tubes  above  this  to  the  fifth  row  were  closed  by 
cast  iron  neck  pieces  screwed  into  the  ends  with  cast  iron  covers 
bolted  on.  The  fifth  and  sixth  rows  had  a  passage  from  one  to 
he  other  provided  in  front,  these  two  rows  being  above  the 


THE 


395 


FIG.   186. 


FIG.   187. 


FIG-.   188. 


FIG.   189. 


396 


THE  PRACTICAL  PHYSICS  OF 


water  line,  so  that  the  steam  should  pass  from  the  collecting 
pipe  through  these  tubes  consecutively  to  the  steam  drum.  The 
connections  between  the  tubes  are  not  so  complete  in  this  case 
as  in  Root's  boiler,  and  promise  difficulty  in  circulation  of  the 
water.  The  form  shown  in  1875  was  preferable  in  this  respect. 
The  Howard  boiler  arranged  for  marine  use  was  illustrated  in 
Mr.  J.  Fortescue  Flannery's  paper  u  On  the  Construction  of 
High-Pressure  Steam  Boilers"  (Min.  Proc.  Inst.  C.E.,  Vol.  liv., 
P-  123). 

It  was  introduced  into  the  steamers  "  Fairy   Dell/'  "  Mere- 
dith," and  "  Marc  Antony"  about  the  year   1870,  but  was  not 


KIG.   190. 

very  successful.  Particulars  of  the  boilers  of  the  *'  Fairy  Dell  " 
and  "  Marc  Antony  "  were  given  in  Engineering  of  3rd  March 
1871  (Vol.  xi.,  p.  155),  and  by  the  late  Mr.  W.  Parker  in  Min. 
Proc.  Inst.  C.E.,  Vol.  xcix.,  p.  106. 

Watt's  Boiler. — A  marine  boiler  of  the  horizontally  inclined 
water  tube  design  was  patented  by  Mr.  John  Watt  in  1871  (No. 
3011  ;  see  also  No.  14430,  1890),  and  brought  forward  by  him 
in  a  paper  "  On  Water-tube  Boilers  "  read  to  the  Liverpool  Poly- 
technic Society  in  1874  (see  Engineering,  27th  March,  1874,  PP- 
234-236).  It  was  also  described  in  Mr.  Flannery's  paper  above 
quoted.  Figs.  191  and  192  illustrate  this  boiler. 

The  horizontally  inclined  tubes  were  connected  at   each  end 


THE  MODERN  STEAM  BOILER. 


397 


to  a  Hat  rectangular  chamber  embracing  the  whole  of  the  tubes 
in  one  boiler.  This  chamber  was  stayed  to  give  it  the  neces- 
sary strength,  the  stay  bolts  also  serving  as  studs  for  fastening  on 
the  covers  placed  opposite  the  ends  of  the  tubes  on  the  outside 
of  both  chambers. 

Suckling's  Boilers, — Some  interesting  features  were  embraced 
in  the  boiler  designed  by  Mr.  N.  J.  Suckling  and  illustrated  in 
the  Engineer  of  28th  February,  1873. 

Suckling's  British  patents  are — 1872  (Nos.  2747  and  3893), 
and  1875  (No.  3494).' 

In  his  paper  "  On  Modern  Systems  of  Generating  Steam," 
read  to  the  Society  of  Engineers,  London,  on  4th  May,  1874 
(see  the  Engineer,  2Qth  May,  1874,  and  Transactions  of  the 


nn. 


FIG.   191. 


KIU.   192. 


Society  of  Engineers),  Mr.  Suckling  set  forth  many  of  the  re- 
quirements of  a  good  boiler  ;  but  it  almost  seemed  as  if,  in  order 
to  secure  some  of  these,  he  had  been  compelled  to  sacrifice  others 
which  are  quite  as  necessary.  Mr.  Suckling's  boiler,  shown  in 
Figs.  193,  194  and  195,  was  composed  of  horizontally  inclined 
generating  tubes  arranged  over  the  furnace  so  as  to  "  break 
joint  "  or  cause  the  gases  to  take  a  zig-zag  course  in  moving 
upwards.  The  front  ends  of  the  tubes  had  heavy  wrought  iron 
llanges  screwed  on,  and  the  back  ends  had  wrought  iron  rings 
welded  in,  to  which  were  secured  wrought  iron  covers  bolted 
on  and  having  each  a  screwed  pipe  connection  at  the  centre. 
Small  straight  or  curved  pipes  led  from  these  to  large  external 
tubes  which  acted  as  downcomers  for  the  water  and  separators 
of  steam  and  water.  Every  generating  tube  drew  its  own 


398 


THE  PRACTICAL  PHYSICS  OF 


LONGITUDINAL  SECTION 


FIG.   193. 


FIG.   194. 


FIG.   icj5. 


THE  MODERN  STEAM  BOILER. 


399 


supply  of  water  from  the  downcomer,  and  all  the  joints  were 
outside  the  boiler,  but  the  loss  of  heat  by  radiation  from  so  large 
an  area  of  outside  connections  must  have  been  considerable. 

Hardingham's  Boiler. — Patents  for  concentric  tube  boilers 
of  the  horizontally  inclined  type  were  taken  out  in  1882  by 
R.  H.  Brandon  (for  C.  Camper)  on  I2th  April  (No.  1745),  and 
by  G.  G.  M.  Hardingham  on  i8th  October  (No.  4956).  The 
former  one  does  not  seem  to  have  been  brought  out,  but  Mr. 
Hardingham's  boiler  has  been  described  in  Engineering  of  nth 


FIG.    196. 

January,  1884,  and  put  on  the  market.  Improvements  were 
patented  in  January,  1884  (No.  565).  The  water  tube,  which  is 
the  outer  tube,  is  screwed  or  fastened  otherwise  to  the  socket 
plate  of  a  cast  iron  box  and  the  inner  or  fire  tube  is  packed  by 
a  screw  gland  to  the  outer  face  of  the  same  box.  The  boxes  are 
arranged  so  as  to  leave  a  passage  for  the  steam  and  water  up  to 
the  steam  drum.  See  Fig.  196. 

The  course  of  the  hot  gases  is  as  shown — first,  directly  up- 
wards over   the  outsides  of  the  water  L-tubes   and  then  to  the 


4<x> 


THE  PRACTICAL  PHYSICS  OF 


front  or  elevated  end  of 
the  boiler,  and  downwards 
through  all  the  inner  tubes 
to  a  flue  at  the  back.  Pro- 
vision is  made  for  water 
circulation  and  the  boiler 
is  well  proportioned. 

Lane's  Boiler.  —  Mr.  H. 
Lane  took  out  a  patent  in 
January,  1883  (No.  209),  for 
a  horizontally  inclined  tube 
boiler  with  box  headers, 
very  like  those  of  the  Root 
boiler,  but  he  followed  in 
May,  1883  (No.  2405),  and 
later  (No.  4033)  with  patents 
for  the  boiler  shown  in  the 
Figs.  197  and  198.  In  this 
design  the  horizontally  in- 
clined tubes  are  closed  by 


'HE  MODERN  STEAM  BOILER. 


401 


a  screwed  plug  at  their  lower  ends  and  have  each  an  internal 
circulating  tube  for  water.  At  the  front  is  an  upright  square 
chamber  having  a  vertical  partition,  dividing  it  into  the  compart- 
ments internally.  The  inner  circulating  tubes  are  fastened  into 
this  partition  and  the  outer  tubes  to  the  back  of  the  chamber. 
A  steam  drum  is  placed  on  the  top  of  the  chamber,  and  the 


upward  current  of  steam  and  downward  current  of  water  do 
not  interfere  with  one  another.  Dimensions  and  details  are 
given  in  a  description  in  Vol.  ii.  of  D.  K.  Clark's  "  Steam 
Engine,"  pp.  773~777- 

Steinmiiller  Boiler, — The  boiler  brought  out  in  Germany  by 
Messrs.  L.  and  C.  Steinmiiller,  of  Gummersbach  (Rhine  Pro- 
vince), was  patented  in  this  country  in  1876  (No.  3646).  1884 


402 


THE  PRACTICAL  PHYSICS  OF 


(No.   11105),   J889  (No.   5868),  and  1890  (No.   1348).     It  is  to 
some  extent  like  Watt's  boiler,  having  flat  stayed  chambers  at 


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each  end  of  the  horizontally  inclined  tubes.  The  steam  dome 
is,  however,  placed  horizontally  (not  inclined,  as  in  Watt's  boiler) 
in  the  centre  between  two  boilers,  and  the  generating  tubes  are 


THE  MODERN  STEAM  BOI-LER. 


403 


grouped   around   it   on  its   under  side.       Figs.   199,   200,  201, 

and  202  show  this  boiler. 

For  marine  use  the  out- 
side vertical  row  of  tubes  is 
arranged  so  that  the  tubes 
touch,  a  small  neck  piece 
connecting  alternate  tubes 
with  the  Hat  chamber  wall 
so  as  to  have  sufficient  metal 
between  the  openings  for 
strength. 

The  Eutiner  Boiler,  - 
Another  boiler  of  this  class 
in  use  in  Germany  is  the 
Biittner  boiler,  patented  in 
this  country  in  1873  (No. 
412),  and  by  H.  Simon  (for 
FIG  20I  F.  L.  A.  Buttner)  in  1879 

(No.    566),   and    1891    (No. 

10237).     It  has  the  horizontally  inclined  tubes  fastened  into  flat 

chambers  at  each  end  like  the 

Watt,  Steinmuller,  Heine,  and 

other  boilers.     There  is,  how- 
ever, a  row  of  shorter  tubes 

immediately  over  the  lire  con- 
nected to  a  common  transverse 

tube  at  their  lower  ends,  this 

transverse   water   tube    being 

connected    to    a  similar  tube 

at  the  foot  of  the  back  header. 
The  Niclausse  Boiler. — The 

Niclausse  boiler  was,  accord- 
ing   to    M.    Bertin    ("  Marine 

Boilers,"    p.  268),    developed 

from  the  Collet  boiler,  so  that 

its    introduction    dates    from 

the  publication  of  the  Collet 

design,  although  it  has   been 

greatly  altered  in  details.     As 

now  known,  the  Niclausse  boiler  is  composed  of  tubes  (of  3  to 


4°4 


THE  PRACTICAL  PHYSICS  OF 


4  inches  diameter)  slightly  inclined  from  the  horizontal,  with 
headers  at  only  one  end,  the  other  end  of  the  tubes  being  left 
free,  so  that  there  is  no  rigidity  to  resist  expansion  lengthwise. 
The  free  end  of  each  tube  is  closed  by  a  screwed  cap,  and  the 


203. 


front  end  is  secured  by  two  coned  joints  to  both  outer  and  inner 
walls  of  the  header,  although  it  communicates  only  with  the 
inner  of  the  two  chambers  or  passages  into  which  the  header  is 
divided  by  a  partition.  The  outer  chamber  is  in  communication 
with  the  smaller  tubes,  of  which  one  is  inserted  concentrically 


THE  MODERN  STEAM  BOILER. 


4°5 


for  circulation  of  water,  in  each  of  the  larger  generating  tubes. 
At  the  top  of  the  header  is  the  steam  drum,  and  as  the  water 
level  stands  at  about  the  centre  of  this  cylinder,  circulation 
of  the  water  commences  as  soon  as  heat  is  applied  to  the  tubes. 
The  water  flows  down  the  outer  or  downcast  half  of  the 
header,  through  the  small  inner  tubes,  which  project  nearly 
the  full  length  of  the  generating  tubes,  and  back  by  the  outer 


FIG.    205. 

tubes,  the  steam  and  foam  escaping  by  the  upcast  half  of  the 
header.  The  constructional  details  have  been  arranged  with 
great  ingenuity  in  order  to  simplify  both  erection,  examina- 
tion, and  repair  of  the  boiler.  The  method  of  attaching  the 
tubes  to  the  header  by  means  of  coned  joints  and  "  lanternes  " 
(which  the  sleeves  forming  continuations  of  the  tubes  are 
called)  is  a  salient  feature  of  this  boiler,  and  this  improve- 
ment over  the  original  Collet  design  is  due  to  the  Messrs. 


406' 


THE  PRACTICAL  PHYSICS  OF 


Niclausse.     It  has  been  fully  described  by  Mr.  Mark  Robinson/ 
Mr.  J.  T.  Milton,2  and  M.  Berlin,3  and  is  fairly  represented  in 

1  Trans.  Inst.  N.A.,  1896,  Vol.  37,  p.  119.     Also  British  Assoc.,  1899. 

2  Trans.  Inst.  N.A.,  1894,  Vol.  35.  3  Marine  Boilers,  pp.  271,  272. 


THE  MODERN  STEAM  BOILER. 


407 


section  by  Figs.  203,  204,  and  205,  whilst  the  boiler  as  a  whole 
is  shown  in  Fig.  206. 

Illustrations  of  the  "  Niclausse  "  boiler  will  also  be  found  in 
Engineering,  Vol.  lx.,  page  91,  and  of  the  Niclausse  small  tube 
boiler,  in  the  Electrical  Engineer  of  I3th  October,  1899,  page  461. 

Records  of  tests  will  be  found  in  Chapter  IX.,  and  in  the 
papers  quoted  above,  and  some  interesting  points  of  comparison 
between  this  and  other  boilers  will  be  met  with  in  Mr.  Mark 
Robinson's  paper  read  at  the  1899  meeting  of  the  British  Asso- 
ciation. The  first  British  patent  due  to  M.  Collet  is  dated 
i5th  February,  1878  (No.  644),  but  the  subsequent  patents  refer- 
ring to  the  Niclausse  boiler  are  1891  (No.  1052),  1893  (Nos.  10136 


FIG.   207. 

and  23841),  1894  (No.  16472),  1898  (Nos.  13031  and  18166), 
1900  (No.  1382).  These  show  the  working  out  of  the  tube  head 
design  and  other  important  details. 

The  Phlegcr  Boiler. — The  Phleger  boiler  is  of  American  origin, 
and  possesses  some  distinct  features  from  other  horizontal  tube 
boilers.  The  fireplace,  including  the  bars,  is  constructed  (except 
at  the  two  sides)  entirely  of  tubes  2  inches  diameter,  laid  flat  to 
form  fire-bars,  and  then  bent  up  from  the  back  of  the  grate  at  an 
angle  to  form  the  roof  of  the  fireplace.  At  their  lower  ends 
they  are  expanded  into  a  narrow  strip  of  plate,  which,  with  a 
cover  semi-circular  in  section,  forms  the  feed  connection.  The 
top  ends  lead  into  a  similar  chamber,  in  which  there  are  also  the 
ends  of  other  two  rows  of  horizontal  tubes,  which  tubes  extend 


408 


THE  PRACTICAL  PHYSICS  OF 


back  as  far  as  is  required.  Above  these  are  other  two  rows  of 
horizontal  tubes  connecting  with  another  chamber  in  front,  from 
which  a  branch  leads  to  the  steam  drum  above.  The  connec- 
tions of  the  tubes  place  them  in  series,  except  that  the  steam 
and  water  from  the  one  row  below  and  above  the  fire  pass 
through  the  upper  four  rows  in  pairs — the  lower  pair  taking  the 
current  to  the  back  and  the  upper  to  the  front  of  the  boiler. 
The  boiler  is  illustrated  in  Fig.  207. 


FIG.   208. 

This  boiler  figured  in  the  tests  made  at  the  American  Institute 
Exhibition  in  1871,  but  it  does  not  appear  to  have  been  intro- 
duced into  Britain. 

Heine  Boiler. — The  Heine  boiler  is  used  in  both  Germany  and 
America.  It  was  patented  in  Britain  by  F.  C.  Glaser,  for  H. 
Heine,  in  1881  (No.  3181),  but  does  not  seem  to  have  been 
adopted  to  any  extent  here.  It  is  shown  in  Fig.  208,  and  is  one 
of  the  horizontal  water-tube  boilers  with  water-legs  or  chambers 
riveted  to  each  end  of  cylindrical  steam  and  water  shells.  These 


THE  MODERN  STEAM  BOILER. 


409 


shells  range  from  24  to  48  inches  diameter,  and  for  all  sizes 
above  200  H.P.,  two  shells  are  used,  a  steam  drum  being  in  that 
case  placed  above  and  across  the  front  ends  of  these  two 
cylinders. 

Poole  Boiler  and  Seaton  Boiler. — The  Poole  boiler,  also  intro- 
duced in  America,  Fig.  209,  shows  the  same  general  design,  with 
the  water-legs  attached  to  one  cylindrical  vessel  or  drum,  whilst 
other  modifications  are  seen  in  the  boiler  proposed  by  Mr.  A.  E. 
Seaton  in  1893  (No.  19853),  as  described  by  Mr.  J.  T.  Milton  in 


FIG.   209. 


Trans.  Inst.  N.  A.,  1894,  and  shown  in  Fig.  210,  in  the  Lagrafel 
D'Allest  boiler  and  the  Oriolle  boiler. 

Lagrafel  D'Allest  Boiler.— The  Lagrafel  D'Allest  boiler,  as 
now  used  in  the  French  Navy,  is  the  outcome  of  numerous 
improvements,  the  original  boiler  having  been  introduced 
there  about  the  year  1869.  The  modern  Lagrafel  D'Allest 
boiler  was  patented  in  England  in  1888  (No.  11160),  whilst 
the  dates  of  French  improvements  are  recorded  in  M. 
Bertin's  "Marine  Boilers,"  p.  249.  Fig.  211  illustrates  this 
boiler. 


4io 


THE  PRACTICAL  PHYSICS  OF 


THE  MODERN  STEAM  BOILER. 


411 


Oriolle   Boiler. — The  Oriolle  boiler   is  also  of  French  origin, 
and  is  used  in  the  French  Navy.     The  British  patents  are  dated 


Longitudinal  section. 


Half  end  elevation.  Half  transverse  section. 


27th  June,  1887  (No.  9121),  and  i8th  April,  1890  (No.  5922).  It 
is  illustrated  in  Fig.  212,  which  shows  the  form  used  in  French 
torpedo  boats. 


4I2 


THE  PRACTICAL  PHYSICS  OF 


The  Kelly  Boilet. — An  American  boiler  of  this  name  ("  Kelly") 
is  described  by  Mr.  D.  K.  Clark  in  "  The  Steam  Engine,"  &c., 
and  appeared  amongst  the  boilers  tested  at  Philadelphia  in  1876. 
Its  wrought  iron  horizontally  inclined  tubes  were  screwed  into 
a  cast  iron  header  at  the  front  end  and  closed  at  the  back  end, 
towards  which  they  inclined  downwards.  See  Fig.  213.  The 
tubes  had  each  a  diaphragm  plate  inserted  internally  in  order  to 
ensure  circulation  of  water  in  them.  There  seems,  however,  to 
be  another  water-tube  boiler  known  as  Kelly's  boiler,  or  as  the 
"  National  "  boiler  in  America.  This  one  has  headers  at  both 
ends  of  the  horizontally  inclined  tubes,  somewhat  after  the 
Babcock  and  Wilcox  and  similar  designs.  This  boiler  seems 


to  have   been  patented  in  Britain  in  1886  (No.  12697)  and  1887 
(No.  11141). 

Diirr  Boiler. — The  boiler  made  by  Messrs.  Diirr  and  Co.,  of 
Ratingen,  has  some  features  in  common  with  the  former  of  the 
Kelly  boilers,  as  well  as  with  those  of  Alban,  Lane,  and  Niclausse. 
The  horizontally  inclined  tubes  are  connected  only  at  the  front 
end  to  a  "  header,"  which  is  a  water  chamber  extending  over  the 
front  of  the  boiler.  This  chamber  is  divided  internally  into  two 
parts  by  a  movable  diaphragm  plate  which  is  formed  of  several 
pieces,  each  being  secured  in  place  by  means  of  nuts  threaded 
on  screws  formed  on  the  stays.  The  horizontally  inclined  tubes 
are  closed  at  their  lower  ends,  where  they  are  slightly  reduced 
in  diameter,  by  end  plates  fitting  with  conical  joints  and  kept  in 


THE  MODERN  STEAM  BOILER. 


413 


place  by  bolts.  Internal  concentric  tubes  are  fixed  to  the 
diaphragm  plate  and  communicate  with  the  front  division  of 
the  water  chamber.  These  internal  circulating  tubes  reach  to 
nearly  the  end  of  the  larger  tubes,  and  as  the  normal  water- 
level  of  the  boiler  is  at  about  the  centre  of  the  steam  chamber 
above,  the  circulation  of  water  is  similar  to  that  of  the  Niclausse 
boiler.  Figs.  214,  215,  216,  and  217  show  this  boiler.  At  the 
sides,  the  water-tubes  are  bent  so  as  to  bring  them  together  to 
form  a  water  wall,  and  above  the  water  level  two  or  three  rows 
of  concentric  tubes  are  employed  as  superheaters  for  the  steam. 
This  boiler  was  fully  described  by  Mr.  J.  T.  Milton  in  Trans. 


FIG.   214. 


Inst.  N.  A.,  1894.  English  patents  for  the  Diirr  boiler  are  dated 
in  1886  (No.  17123),  1888  (No.  12060),  1889  (No.  13222),  and 
1890  (Nos.  6398  and  19082),  1893  (No-  i4745)>  1895  (No.  1716), 
1896  (No.  24787). 

As  made  by  the  Societe  Industrielle  de  Paris,  the  Diirr  boiler 
ttfts  some  improvements  in  details,  and  is  furnished  writh  a  feed- 
heater.  It  shares  with  the  Niclausse  boiler  the  feature  of  being 
able  to  do  without  expanded  or  other  tube  joints,  the  steam 
pressure  tending  to  hold  the  tubes  firmly  in  position  and  to 
tighten  the  joints. 


THE  PRACTICAL  PHYSICS  OF 


felG.   21 v 


FIG.   2l6, 


THE  MODERN  STEAM  BOILER. 


415 


The  Hornsby  Boiler. — The    Hornsby  boiler,  which   was    pre- 
viously known  as  the  Mills  boiler,  has  some   excellent  features, 


FIG.  217. 


and  is  made  either  with  a  brick-lined  or  a  water-lined  furnace, 
according  to  the  class  and  quality  of  the  fuel  to  be  used.  The 
horizontally  inclined  tubes  are  fastened  into  wrought  steel 


4i6 


THE  PRACTICAL  PHYSICS  OF 


headers   which   are   formed    by  hydraulic  pressure  from  mild 
steel   plates,   and   the   openings    opposite   the   tube    ends    are 


FIG.    2 1 8. 

closed  by   internal  safety  hand-hole  doors  of   mild  steel  with 

external  caps.  The  cylin- 
drical steam  and  water 
drum  surmounts  the  tubes, 
and  the  vertical  tubes  con- 
necting it  with  the  headers 
allow  freedom  of  expan- 
sion in  the  generating  tubes. 
Figs.  218  and  219  represent 
this  boiler. 

The  British   patents   for 
this    boiler    are    dated    in 
1888  (No.  7077),  1889  (Nos. 
FIG.  219.  9938  and  11488),  and  1893 

(No.  949). 
The  Towne  Boiler. — The  Towne  boiler  has  two  sets  of  inclined 

tubes,  which  are  inclined  alternately  from  side  to  side  across  the 


THE  MODERN  STEAM  BOILER. 


417 


top  of  the  tire,  and  are  connected  to  Hat  chambers  which 
are  bent  at  the  centre  of  their  height  in  order  to  meet  the 
incoming  tubes  at  right  angles.  Fig.  220  shows  this  boiler, 
which  has  been  introduced  into  launches  and  gunboats  in 
America,  and  was  patented  in  Britain  in  1890  (No.  5064). 
There  appear  to  be  other  boilers  claiming  the  same  design,  as 
one  similar  to  Fig.  220  was  illustrated  in  Electrical  Industries,  a 


New  York  paper  of  December,  1892,  Vol.  iii.,  No.  12,  under  the 
name  of  the  Worthington  patent  sectional  water-tube  boiler, 
manufactured  by  the  New  York  Safety  Steam  Power  Company, 
and  patented  in  Britain  in  1894  (No.  16750).  A  modification  of 
this  type  of  boiler  was  patented  by  A.  Montufet  in  January, 
1897  (No.  429). 

Rainess  Boiler. — The  only  other  boiler  of  this  class  which  we 
illustrate  here  is  the  one  patented  by  F.  E.  Rainey  in   1896  (No. 


418 


THE  PRACTICAL  PHYSICS  OF 


2428).     Fig.  221  shows  this   design,  from  which  it  will  be  seen 
that,  in  addition  to  the  horizontally  inclined  tubes  arranged  in 


headers,  so  as  to  form  a  flattened  spiral,  there  are  "  riser  tubes," 
one  from  each  header,  going  directly  to  the  steam  chamber,  and 


THE  MODERN  STEAM  BOILER.  419 

allowing  the  steam  brought  into  the  header  to  escape  upwards, 
while  the  water  flows  on  through  the  horizontal  tubes. 

The  horizontal  form  of  the  Peterson  boiler  will  be  found 
later  (see  p.  463). 

Modifications  of  the  Horizontal  Tube  Boiler. — The  modifications 
of  the  horizontal  water-tube  boiler  which  have  been  proposed 
are  too  numerous  to  be  noticed  in  detail.  Amongst  the  more 
important  of  these  are  the  boiler  of  G.  Sinclair,  patented  in 
1872  (No.  3726)  and  1873  (No.  3693),  which  was  made  for  some 
years  at  Albion  Boiler  Works  in  Leith,  Scotland,  and  was  de- 
scribed by  D.  K.  Clark  in  his  "  Steam  Engine,"  &c.,  Vol.  ii., 
p.  772  ;  Griffith's  boiler,  patented  in  1873  (No.  2170),  as  made 
by  J.  Halliday  in  Manchester  ;  Yarrow's  boiler  of  1879  (No. 
316)  ;  Lloyd's  of  1884  (No.  11633)  ;  the  De  Naeyer  boiler  of 
1886  (No.  2769),  introduced  and  'manufactured  in  Belgium  ; 
Sellers  of  1891  (No.  20954),  which  was  introduced  in  America, 
and  is  illustrated  in  Electrical  Industries  of  New  York,  Vol.  iii., 
No.  12,  p.  329  ;  Anderson  and  Lyall's,  patented  in  1892  (No. 
12609),  described  in  Mr.  J.  T.  Milton's  paper  "On  Water-tube 
Boilers"  (Trans.  Inst.  Naval  Architects,  1894);  the  Coignet ' 
boiler,  patented  in  1892  (No.  15168),  and  1893  (No.  5145)  ;  the 
Zell  boiler  and  the  Gill  boiler,  both  shown  at  the  Chicago  Exhi- 
bition in  1893,  and  illustrated  in  the  Engineer,  August,  1893  (PP- 
118-170). 

The  Charles  and  Babillot  boiler,  illustrated  in  Bertin  and 
Robertson's  "  Marine  Boilers,"  p.  281,  which  was  patented  in 
Britain  in  1891  (No.  16565),  is  a  novel  arrangement  of  concentric 
tubes  horizontally  inclined. 

In  addition  to  these  and  many  similar  designs  there  are 
several  boilers  having  a  single  header  or  vertical  water  chamber 
with  horizontally  inclined  tubes  bent  so  that  both  ends  of  the 
tubes  are  connected  to  it.  Of  this  design  are  the  boilers 
patented  by  A.  Greenwood  in  1877  (No.  168),  A'.  R.  Thirion  in 
1890  (No.  8987),  and  E.  A.  Mayer  in  1892  (No.  13192).  The 
Solignac  boiler,  illustrated  in  the  Mechanical  Engineer,  Vol.  i., 
p.  600,  is  another  example,"  and  an  elaborate  modification  of 
this  design  is  known  as  Petit  and  Godard's  boiler,  and  is 

1  See  Min.  Proc.  Inst.  C.  E.,  Vol.  cxiii.,  p.  431  ;  Le  Genie  Civil,  Vol.  xxii.. 
i«93,  P-  395- 

2  The  Solignac  boiler  was  patented  in  Britain  in  1894  (No.  20466). 

P   2 


426 


THE  PRACTICAL  PHYSICS 


illustrated  in  Berlin  and  Robertson's  "  Marine  Boilers,"  p.  265, 
but  the  original  was,  according  to  M.  Chasseloup-Laubat,  intro- 
duced by  M.  Sochet  in  1855. *  The  comparatively  recent 
Thornycroft- Marshall  boiler,  Figs.  222  and  223  belongs  to  the 
same  class. 

Such  designs  as  that  of  J.  M.  Stratton,  of  1890  (No.  5633), 
although  special,  may  also  fall  within  the  class  of  horizontally 
inclined  water-tube  boilers. 


Horizontal  Chamber  Boilers.—  Allied  to  this  class  are  boilers 
formed  of  a  number  of  horizontal  cylindrical  chambers  con- 
nected together,  usually  by  means  of  short  vertical  branches  or 
tubes.  This  design  is,  in  fact,  a  development  of  that  of  Woolf, 
but  the  number  of  tiers  of  chambers  of  comparatively  small 
diameter  has  been  increased  since  his  day,  and  cast  iron,  as  the 
material  of  construction,  has  been  abandoned.  Instances  of 
this  design  are  to  be  found  in  the  boilers  proposed  by  J.  Bray  shay 
in  1856  (No.  1738),  L.  Durancl,  1858  (No.  1063),  J.  Howden,  1860 
(No.  2854),  B.  Illingworth,  1876  (No.  3460),  1879  (No.  1563),  J.C. 


1  See  Les  Chaudieres  Marines,  by  M.  L.   De  Chasseloup-Laubat.     Paris  : 
[897,  pp.  n,  72.     Also  Bertin  and  Robertson,  p.  293. 


THE  MODERN  STEAM-BOILER. 


421 


Mewburn,  1880  (No.  2348),  G.  H.    Lloyd,    1881  (No.  5741),  and 
others. 

The  boiler  patented  by  Mr.  Howden  was  illustrated  by  him  in 
his  paper  "  On  the  Comparative  Merits  of  Cylindrical  and  Water- 
tube  Boilers  for  Ocean  Steamships, "in  Trans.  Inst.  Naval  Archi- 
tects for  1894  (Plate  Ixiii.,  Figs.  7  and  8),  and  similar  boilers 
were  also  subsequently  introduced  for  land  tise  by  Messrs. 
Hawksley,  Wild  and  Co.,  of  Sheffield  ;  Thomas  Piggott  and  Co., 


FIG.   223. 


of  Birmingham  ;  and  the  Crosland  Company  of  Manchester,1 
illustrations  of  whose  boilers  will  be  found  in  Engineering  of 
1874  and  1875.  What  may  be  called  an  exaggeration  of  this 
design,  simply,  however,  on  account  of  the  increased  diameter  cf 
the  chambers,  will  be  seen  in  the  so-called  "  Howard  "  boiler 
constructed  at  Barrow  for  the  steamer  "  Red  Rose,"  this  boiler 
being  illustrated  in  Mr.  Flannery's  paper  in  Min.  Proc.  Inst.  C.  E., 
Vol.  liv.,  p.  123  (in  Figs.  3  of  Plate  6)  ;  and  in  the  Wigzell 

1  The  patents  of  Hawksley  and  Wild  are— 1869  (No.  2922),  1872  (No.  3207), 
of  the  Kesterton  boiler,  1872  (No.  3870),  1873  (No.  2497),  and  of  the  Crosland 
boiler,  1869  (No.  2083),  1870  (No.  2818),  1871  (No.  2749),  *872  (Nos.  1962  and 
3310),  1873  (Nos.  1249  and  2614). 


422  THE  PRACTICAL  PHYSICS  OF 

boiler,    described    by  the   same   author    in    Trans.    Inst.    Naval 
Architects  for  1876 l  (Vol.  xvii.,  p.  274,  Fig.  14). 

Another  arrangement  of  horizontal  cylindrical  chambers 
which  has  had  many  advocates  is  that  in  which  the  chambers  are 
placed  concentrically.  A  glance  through  the  records  of  the 
Patent  Office  shows  that  this  was  from  early  days  a  favourite 
plan.  It  was,  perhaps,  suggested  by  Trevithick's  boiler  of  1802, 
which  was  subsequently  known  as  the  "  Cornish  "  boiler  ;  and, 
in  fact,  that  boiler  shows  the  plan  in  its  most  simple  form,  but  it 
has  been  developed  so  that  several  thin  layers  of  water  are 
exposed  to  heat,  in  order  to  facilitate  evaporation.  A  typical 
example  of  this  design,  and  what  was  perhaps  the  latest  attempt 
to  utilise  the  plan  in  marine  work  is  found  in  Howden  and 
Morton's  boiler,  which  was  fitted  in  the  s.s.  "  Ailsa  Craig  "  in 
1859,  and  is  described  in  Mr.  Howden's  paper  in  Trans. 
Inst.  Naval  Architects  for  1894  (Vol.  xxxv.,  Plate  Ixi.,  Figs. 
5  and  6). 

Vertical  Water-Tube  Boilers. — The  natural  action  of  boiling, 
with  the  vertical  ascent  of  the  heated  water  and  steam  bubbles, 
doubtless  suggested,  at  an  early  period,  the  suitability  of  vertical 
water-tubes  for  the  construction  of  vessels  in  which  such  action 
was  to  take  place.  In  the  history  of  this  design  R.  Trevithick's 
patent  of  1815  (No.  3922)  has  been  supposed  to  have  introduced 
vertical  tubes  closed  at  the  lower  end  and  hanging  by  their 
upper  end  from  a  tube  or  water  chamber,  the  pendant  part  being 
in  the  combustion  space,  but  a  careful  study  of  that  specihcation 
shows  that  it  disclosed  no  such  design.  Trevithick  had  patented 
in  1831  (No.  6080)  the  use  of  a  form  of  concentric  vertical  tubes, 
and  others  had  previously  brought  out  smaller  vertical  water 
tubes  with  concentric  tubes,  so  that  when  Jacob  Perkins  followed 
in  July  of  the  same  year  with  his  patent  (No.  6128)  for  the 
hanging  tubes,  each  containing  an  internal  tube  open  at  both 
ends  for  water  supply  and  circulation,  only  a  small  part  of  the 
main  idea  had  been  published  by  Trevithick. 

From  what  is  said  by  Tredgold  ("  The  Steam  Engine,"  ist 
ed.,  p.  135  ;  new  ed.,  1838,  p.  128)  it  would  appear  that  Count 
Rumford  originated  the  hanging  tube  design,  if  not  in  the  boiler 
which  he  put  up  in  the  Royal  Institution  in  1796,  at  any  rate 

1  See  also  Engineering  of  28th  April,  1876. 


THE  MODERN  STEAM  BOILER.  423 

in  the  model  boiler  which  he  presented  to  the  French  Institute 
in  1806,  which  latter  Tredgold  describes  minutely.  This,  how- 
ever, seems  not  to  have  been  generally  known  either  here  or  in 
France. 

Perkins'  idea  wras  adopted  successively  by  R.  Prosser  in  1839 
(No.  7969),  P.  F.  Joly  in  1857  (No-  2443)>  and  E.  Field  in  1862 
(No.  2956),  and  1865  (No.  2661),  to  the  latter  of  whom  is  gene- 
rally ascribed  the  credit  of  first  forming  the  top  end  or  "  mouth" 
of  the  inner  tube  of  a  trumpet  shape  or  conical  form,  the  largest 
diameter  being  uppermost.  In  this  country,  consequently,  such 
tubes  are  called  "  Field  "  tubes,  but  in  France  they  are  known 
as  4<  Perkins  "  tubes,  and  in  French  works  on  boilers  are  shown 
both  with  and  without  the  trumpet-mouthed  inner  tube. 

There  seems  to  be  no  reason  why  they  should  not  be  called 
"  Rumford  "  or  "  Perkins  "  tubes  in  this  country  also.  The  only 
notable  boilers  in  which  these  vertical  or  vertically  inclined 
Perkins  tubes  have  been  used  are  those  of  Field,  Allen,  Wiegancl, 
].  Thorn  and  Phillips,  although  several  other  designs  employing 
the  same  form  of  tube  in  a  horizontally  inclined  position  have 
already  been  noticed. 

Clark's  Boiler. — A.  Clark  proposed  in  1822  (-No.  4665)  a  boiler 
for  high  pressure  constructed  principally  of  vertical  copper 
tubes  slightly  curved  in  their  length  to  provide  for  expansion. 
The  tubes  were  connected  to  a  Mat  chamber  below  and  to  a 
"  wagon-head "  above,  an  arrangement  which  does  not  seem 
very  well  adapted  for  high  pressure  ;  but  there  were,  however, 
distinct  downcomer  tubes  provided  between  the  two  chambers, 
so  that  the  design  shows  that  the  importance  of  water  circula- 
tion was  understood  by  some  engineers  at  that  early  date. 

The  boilers  of  Joseph  Moore,  1824  (No.  5032),  and  Paul 
Steenstrup,  1827  (No.  5580)  followed,  the  latter  having  the  tubes, 
set  in  a  rectangular  chamber,  part  of  which  was  below  the  fire 
through  which  the  tubes  projected. 

Eve's  Boiler. — The  boiler  of  Joseph  Eve,  1825  (No.  5297) 
consisted  of  bent  vertical  tubes  attached  above  and  below  to 
horizontal  tubes  of  larger  diameter,  from  which  branches  of 
similar  diameter  led  into  a  steam  chamber  and  a  water  chamber 
below.  One  form  of  it  has  been  represented  by  the  following 
figure,  which  is  taken  from  Mr.  G.  Halliday's  book  on  "  Steam 
Boilers."  Fig.  224. 


THE  PRACTICAL  PHYSICS  OF 


Church's  Boilers. — Wm.  Church  in  1832  (No.  6220)  and  1833 
(No.  6469),  patented  several  forms  of  boilers  employing  vertical 
water  tubes  ;  but  in  the  most  notable  of  his  boilers,  which  was 
used  in  the  early  days  of  steam  road  vehicles,  these  tubes  were 
combined  with  vertical  and  horizontal  chambers,  so  that  the 
boiler  was  practically  a  vertical  shell  or  tank  boiler  with  vertical 
tubes  and  a  water-cased  furnace.  An  illustration  of  the  boiler 
used  in  Church's  steam  coach  will  be  found  in  the  Engineer  of 


FIG.   224. 

lyth  August,  1894,  p.  154,  where  Sir  Frederick  Bramwell's  paper 
on  the  subject  of  the  early  steam  coaches  is  reproduced. 

Summers  and  Ogle's  Boiler. — W.  A.  Summers  and  N.  Ogle  in 
1830  (No.  5927)  brought  out  a  boiler  composed  of  vertical  water 
tubes  with  concentric  flue  tubes  inside.  The  \vater  tubes  were 
connected  at  top  and  bottom  ends  to  transverse  tubes  of  a 
flattened  section,  and  the  internal  tubes  were  so  fastened  outside 
of  the  transverse  tubes  that  they  acted  as  stays  or  ties.  Fig.  225 
shows  this  boiler  in  vertical  section. 

W.  A.  Summers  was  afterwards  associated  with  Andrew  Lamb 
in  the  Lamb  and  Summers  boiler. 


THE  MODERN  STEAM  BOILER. 


425 


Trevilhick's  Boilers.— R.  Trevithick's  patent  of  1831  (No.  6082) 
cannot  accurately  be  described  as  showing  a  boiler  formed  of 
concentric  vertical  water-tubes.  It  showed  rather  a  number  of 
concentric  tubes  grouped  together  to  form  fireplace,  boiler, 
jacket,  condenser,  and  air  vessel.  His  patent  of  1832  (No. 


m 


SIBSBIilBBBiBlHIBBBiii 


ft 

g 

'.  •'      L 

m    \ 

(1 

"11 

=   l    ? 

l 
\ 

R  c: 

F  D  "~ 

j   |    J 

\ 

1 
1 

o  ^ 

=     '^'=. 

T            -             - 

| 

1     1 

§     ^ 

BJ 

^ 

! 

, 

.4 

FIG.   225. 

6308),  however,  contained  an  elaborate  design  for  a  vertical 
water-tube  boiler,  having  vertical  tubes  set  round  the  fire  and 
connected  top  and  bottom  to  tubular  rings,  the  bottom  ring 
being  below  the  grate.  Several  U-shaped  tubes  were  hung  in 
the  combustion  space  over  the  fire  for  the  purpose  of  super- 
heating the  steam  on  its  way  from  the  outside  ring  of  vertical 
tubes  through  the  U -tubes  to  the  engine. 


426 


THE  PRACTICAL  PHYSICS  OP 


Maceroni  and  Squire's  Boiler. — John  Squire  and  Francis 
Maceroni,  first  together  in  1833  (No.  6449),  and  afterwards 
separately  in  1839  (No.  8229),  1842  (No.  9564),  took  out  patents 
for  a  vertical  water-tube  boiler  with  concentric  inner  flue  tubes, 
the  outer  tubes  being  connected  together  by  short  horizontal 


tubes.  Fig.  226  gives  an  illustration  of  this  design  in  perspec- 
tive. In  the  later  patents  some  improvements  in  details  were 
proposed. 

Other  designs  were  proposed  by  J.  McDowal  in  1834  (No. 
6606),  W.  Carpmael  in  1835  (No.  6955),  H.  Elkington  in  1837 
(No.  7305),  and  F.  Hills  in  1839  (No.  7958),  and  1840  (No. 
8495),  none  of  which  demand  particular  notice. 


THE  MODERN  STEAM  BOILER. 


427 


James1 ''Boiler. — In  one  of  the  patents  of  W.  H.  James,  viz., 
that  of  1838  (No.  7854),  however,  there  was  a  design  which 
seems  to  have  been  misunderstood  by  some.  In  this  patent  he 
proposed  to  use  vertical  zig-zag  shaped  tubes,  or  alternately 
spiral  tubes,  connected  top  and  bottom  to  annular  horizontal 
pipes.  The  vertical  tubes  were  to  be  partly  rilled  with  coils  of 
wire,  with  the  idea  of  communicating  heat  more  rapidly  to  the 
water  in  them.  The  mention  of  these  coils  has  evidently  caused 
some  to  imagine  that  this  was  a  coil  boiler,  whereas  its  distinc- 
tive feature  was  the  vertical  zig-zag  or  spiral  tube. 

Craddock' s  Boiler. — In  1840  (No.  8432)  and  1846  (No.  11473) 
Thomas  Craddock  took  out  patents  for  a  vertical  water-tube 
boiler  which  for  a  time  gave  fair  promise  of  good  results.  As 
latterly  made  it  consisted 
wholly  of  vertical  tubes, 
with  a  small  bend  or  curve 
in  the  upper  part  of  their 
length  to  provide  elasticity 
under  expansion,  these  tubes 
being  attached  at  each  end 
to  the  flat  side  of  a  small 
D-shaped  box  or  channel. 
The  lower  channel  was  used 
for  water  supply  and  the  top 
one  for  conveying  steam  to 
a  steam  dome  or  to  the 
engine.  Figs.  227,  228,  and 
229  show  this  boiler,  the  two  latter  as  arranged  for  marine  use,  in 
which  form  it  had  various  trials  in  the  s.s.  "  Thetis  "  about  the 
year  1856.  It  is  evident,  however,  that  there  was  not  sufficient 
freedom  of  circulation  of  water  provided  for  by  the  D-shaped 
connections,  and  that  this  action  is  further  hindered  by  the 
want  of  sufficient  downcomer  channels.  Consequently  serious 
alterations  were  required  in  the  original  "Thetis  "  boilers,  but 
with  these  excellent  evaporative  results  were  obtained  until 
corrosive  action  destroyed  the  vertical  tubes. 

In  1852  (No.  51)  and  1857  (No.  931  and  No.  1162)  Craddock 
turned  to  other  forms  of  boilers,  but  was  not  successful  in 
g:tting  them  introduced.  One  form  of  his  boiler  of  1857  is, 
however,  similar  to  that  of  some  recent  ones. 


Km.  227. 


428 


THE  PRACTICAL  PHYSICS  OF 


FJG.  238 


THE  MODERN  STEAM  BOILER. 


429 


Clarke  and  Motley's  Boiler. — The  patent  of  J.  Winchester,  1842 
(No.  9560),  calls  for  no  further  mention,  but  that  of  Thos. 
Clarke  and  Thos.  Motley,  1849  (No.  12514),  although  never 
introduced  into  use,  has  come  into  some  notice  in  recent  years 
through  abortive  attempts  to  find  in  it  the  original  of  a  design 
which  it  does  not  represent.  This  boiler  was  formed  of  a  main 
vertical  cylindrical  chamber,  from  which  at  the  bottom  two 
semi-circular  or  D-shaped  branches  extended,  one  on  each  side 
of  the  lire  and  just  below  the  fire-bars.  A  single  chamber  of 
the  same  form,  but  of  larger  dimensions,  branched  off  some 
distance  above,  and  these  branch  chambers  were  connected  by 
two  groups  of  straight  water  tubes  inclined  a  little  from  the 
vertical,  one  group  being  on 
each  side  of  the  fire.  The 
two  rows  of  tubes  nearest 
to  the  fire  were  of  larger 
diameter  than  the  rest,  of 
which  the  diameter  was 
decreased  as  the  rows 
receded  from  the  fire.  The 
Fig.  230  illustrates  the  form 
proposed  for  this  boiler. 


FIG.    229. 


It  was  evidently  intended 

to  have  a  supplementary  fire 

under    the    lower    branch 

chambers,  and   a  fan  was 

provided  at  the  bottom  of 

the  ash-pit,  in   which   this 

supplementary  fire  is  shown,  to  supply  air  for  combustion.     The 

spindle  carrying  this  fan  passed  right  up  the  centre  of  the  main 

vertical  chamber,  and  it  carried  paddles  for  forcing  the  water 

into  the  lower  branches,  in  addition  to  a  fan  with  curved  blades 

in  the  steam  space  for  drawing  off  the  steam  and  passing  it  out 

into  steam  pipes.     This  boiler  bore  more  resemblance  to  the 

one  subsequently  patented  by  W.  Johnson  in  1855  -(No.  35)  than 

it  does  to  boilers  of  the  three-chamber  type  introduced  in  1876 

and  in  subsequent  years. 

Johnson's  Boiler. — Fig.    231    shows    Johnson's    boiler,   which 
requires  no  description. 

The  patents  of  W.  E.  Newton,  1849  (No.   12783),  W.  Warne, 


430 


THE  PRACTICAL  PHYSICS  OF 


OP         OOP          O         Ool 


THE  MODERN  STEAM  BOILER. 


431 


1854  (No.  558),  J.  McFarlane,  1854  (No.  1202),  L.  N.  Langlois 
and  J.  B.  Claviers,  1854  (No.  1890),  John  Elder,  1858  (No.  162), 
and  J.  Willcock,  1859  (No.  2614),  all  describe  boilers  of  the 
vertical  water-tube  class,  some  of  which  possess  interesting 
features,  such  as  means  for 
passing  the  currents  of  water 
and  gases  in  opposite  direc- 
tions, tubes  oval  in  section  or 
tapering  in  diameter  upwards, 
the  increased  diameter  being 
above,  combination  of  straight 
and  spiral  tubes,  &c.,  but  none 
of  them  requires  more  par- 
ticular notice. 

Rowan  and  Morton's  Boilers. 
—In  1861  (No.  2207)  ].  M. 
Rowan  and  T.  R.  Horton 
patented  a  boiler  composed  of 
vertical  water-tubes  set  in  rect- 
angular frames  or  leaves  of 
square  section,  formed  by 
channel  irons  and  plates  or  by 
flat  plates  and  angle-irons. 
These  frames  were  set  on  edge 
across  three  cylindrical  water 
chambers  below,  to  which  they 
were  rigidly  attached,  and 
across  their  centre  above  a 
steam  cylinder  with  vertical 
domes  was  placed,  bent  tubes 
from  each  side  branching  out 
horizontally  from  the  steam 
drum  and  entering  the  top  of 
the  frames  vertically.  This 
design  was  a  development  of 
their  cellular  boiler  of  1858  (mentioned  later  on  p.  485),  and  is 
illustrated  by  Fig.  232. 

A  further  development  was  patented  in  1869  (No.  3253),  in 
which  the  frames  or  leaves  were  entirely  abolished,  and  the 
vertical  water-tubes  were  connected  directly  to  the  steam  and 


FIG.   231. 


432 


THE  PRACTICAL  PHYSICS  OF 


water  cylinders,  into  which  all  entered  radially,  the  end  portions 
of  the  tubes  being  bent  to  various  arcs  of  a  circle,  according  to 
their  relative  positions,  for  this  purpose. 


FIG.   232. 

This  design  is  illustrated  in  Figs.  233  and  234.  It  was  fitted 
in  the  steamers  "  Haco,"  "  Propontis,"  "  Nepaul,"  "  Bengal,"  and 
others,  but  on  account  of  an  accident  to  the  boilers  of  the 
"  Propontis/'  shown  in  Fig.  235,  the  exact  cause  of  which  is 
given  in  the  author's  papers  in  Trans,  of  the  Inst.  of  Engineers 


FIG.   233. 


and  Shipbuilders  in  Scotland,  Vols.  xxiii.,  pp.  73: 117,  and  xli., 

pp.  117-121,  the  introduction  of  them  was  prematurely  stopped. 

This  was  undoubtedly  the  first  boiler  of  any  class  in  which 

numbers  of  small  tubes  are  connected  to  cylindrical  chambers 


THE  MODERN  STEAM  BOILER. 


433 


which    they   enter   radially.     This   feature  of  construction  has 
been  widely  copied  since  1869. 

W.  E.  Newton  in  1859  (No.  895)  and  J.  G.  E.  Larned  in  1858 
(No.  2803)  both  proposed  vertical  water-tube  boilers  which  have 
some  points  of  interest.  The  latter  specification,  though  only  a 


A     - 


FIG.   234. 

provisional,  gives  some  figures  of  the  dimensions  of  the  boiler, 
which,  it  is  said,  had  given  120  H.P. 

Green's  Boilei. — E.  and  E.  Green  in  1861  (No.  2671)  patented 
a  boiler  composed  of  vertical  water-tubes  set  in  rows  and 
tapered  in  a  similar  manner  to  that  of  Miller's  cast  iron  boiler 
mentioned  at  page  365.  The  vertical  tubes  were  corrugated  on 
their  outside  surface  in  order  to  increase  the  area  of  heating 


434 


THE  PRACTICAL  PHYSICS  OF 


surface,  and  several  rows  farthest  from  the  fire  were  used  to  heat 
the  entering  feed  water,  these  tubes  being  furnished  with  similar 
scrapers  to  those  used  in  Green's  usual  feed-heater  or  econo- 
miser. 

Williamson's  Boiler. — Several  arrangements  of  a  vertical  water- 
cube  boiler,  the  tubes  inclining  at  a   slight  angle  from  each  side 


FIG.   235. 

of  the  fire,  were  proposed  by  A.  W.  Williamson  in  1861  (No. 
2794)  and  1862  (No.  619).  The  great  point  aimed  at  by  Pro- 
fessor Williamson  in  these  boilers  was  to  have  each  tube  free  to 
expand  without  straining  its  connections,  and  with  this  object 
one  end  of  each  tube  was  closed  and  a  smaller  bent  pipe 
attached  it  to  the  main  steam  connection.  Figs.  236  and  237 
illustrate  this  boiler,  which  was  fitted  into  the  steamer  u  Murillo," 


THE  MODERN  STEAM  BOILER. 


435 


but  was  unsuccessful.    An  account  of  it  is  given  by  Mr.  Howden 
in  Trans.  I.  N.  A.  1894,  Vol.  xxxv.,  p.  311. 

Field's  Boiler. — Several  patents  were  taken  out  by  E.  Field,  with 
some  partners,  in  1862  (No.  2956),  1865  (No.  2661),  1866  (No. 
1694),  and  1867  (No.  1419),  for  boilers  employing  the  hanging 
tube  invented  by  Jacob  Perkins,  with  an  internal  tube  of  which 
the  top  end  was  conically  shaped  to  form  a  "  trumpet-mouth." 
In  the  first  of  these  patents  the  application  of  these  tubes  to 
a  vertical  steam  fire  engine  boiler  is  shown,  but  it  is  in  the  last  of 
them  that  what  is  known  as  the  "'Field  "  boiler  is  set  forth. 


FIG.   236. 


237- 


This  boiler  is  illustrated  in  Fig.  238,  and  a  description  of  it 
will  be  found  in  the  discussion  on  a  paper  on  w?ater-tube  boilers 
by  Mr.  V.  Pendred  in  Trans,  of  the  Society  of  Engineers, 
London,  for  1867,  whilst  the  earlier  boilers  with  "  Field  "  tubes 
are  described  by  Mr.  D.  K.  Clark  in  the  "  Steam  Engine,"  &c., 
Vol.  ii.,  p.  737,  &c. 

A  somewhat  similar  design  was  proposed  by  A.  V.  Newton 
in  1864  (No.  1178),  and  the  Kinsey  "Unit"  boiler,  illustrated 
in  Engineering,  Vol.  viii.,  p.  383-386,  has  some  features  in 
common  with  these  designs. 


436 


THE  PRACTICAL  PHYSICS  OF 


THE  MODERN  STEAM  BOILER. 


437 


TwibilVs  Boiler.— Joseph  Twibill  in  1865  (No.  243)  and  1866 
(No.  2378)  patented  water-tube  boilers  constructed  of  vertically 
inclined  tubes  with  different  degrees  of  inclination.  In  one 
arrangement  the  tubes  forming  the  fireplace  were  placed  in  the 
form  of  a  triangle,  whilst  in  the  flue  or  main  heating  chamber 
they  were  ranged  parallel  to  one  another  and  joined  at  each  end 
by  horizontal  pipes,  with  a  water  chamber  and  a  steam 
chamber  above  the  vertical  tubes.  Another  form,  illustrated  in 
Fig.  239,  had  the  tubes  more  horizontally  inclined  with  vertical 
standpipes,  and  intermediate  horizontal  connections  to  which 


FIG.   239. 

the  ends  of  the  tubes  were  attached.  The  fireplace  was  formed 
of  brickwork,  and  the  steam  and  water  drums  were  carried  by 
the  end  walls  of  the  casing. 

Jordan's  Boiler. — The  boiler  patented  by  T.  B.  Jordan  in  1865 
(No.  2776)  possessed  some  interesting  features.  It  was  composed 
of  vertical  tubes  of  9  inches  in  diameter  and  7  feet  6  inches 
long,  made  of  lap-welded  wrought  iron  J  inch  thick,  and  having 
at  the  top  and  bottom  ends  a  cast  iron  ring  with  side  flanges  to 
which  water  and  steam  branch  pipes  were  attached.  A  wrought 
iron  bolt  tied  the  two  caps  to  the  tube  ;  but  it  was  this  tie-bolt 
which,  as  in  the  case  of  the  Harrison  boiler,  was  most  frequently 
objected  to. 


THE  PRACTICAL  PHYSICS  OF 


Fig.    240    illustrates    this    boiler.      Each   vertical    tube    was 
reckoned    as    equal  to  one    H.P.,    and  some  testimony    to    the 


FIG.  240. 


FIG.   241 


satisfactory  working  of  the  boiler  may  be  found  in  the  discus- 
sion on  Mr.  V.  Pendred's  paper  on  water-tube  boilers,  in  Trans. 
of  the  Society  of  Engineers,  6th  May,  1867. 


THE  MODERN  STEAM  BOILER. 


439 


Howuni's  Boiler. — Jas.  Howard  and  E.  T.  Boustield  took  out  a 
number  of  patents  for  what  was  known  as  the  Howard  vertical 
tube  boiler,  manufactured  and  used  at  Messrs.  J.  and  F.  Howard's 
Britannia  Works  at  Bedford.  These  patents  are  dated  1866 
(Nos.  226  and  1811),  1867  (No.  76),  1868  (Nos.  430  and  3468), 
and  later  years,  and  the  boiler  consisted  of  vertical  tubes, 
connected  top  and  bottom  by  transverse  tubes,  and  having 
concentric  circulating  tubes  inside  the  vertical  tubes  extending 
up  to  the  water  level  of  the  boiler.  Figs.  241  and  242  show  this 


0© 

0© 
0© 

©G 


boiler,  which  gave  fairly  good  results,  some  record  of  which  will 
be  found  in  Mr.  Pendred's  paper  and  discussion  above  quoted. 

Although  one  section  of  the  Howard  vertical  tube  resembles 
the  hanging  tube  of  Perkins  with  its  internal  tube,  it  is  evident 
that  this  design  is  only  approximately  similar  to  Perkins'. 

\Vicgand  Boiler. — In  the  case  of  the  Wiegand  boiler,  intro- 
duced in  America,  but  patented  in  Britain  in  1868  (No.  1365) 
and  1870  (Nos.  1856  and  3390),  we  have,  however,  a  direct 
application  of  the  Perkins  tubs.  This  boiler  is  illustrated  in 
Fig.  243.  It  consisted  at  first  of  rectangular  boxes,  or  small  tanks, 
from  which  pendant  tubes  hung  vertically  downwards,  each  of 
these  tubes  having  an  internal  tube  provided  with  external  tins 


THE  PRACTICAL  PHYSICS  OF 


or  feathers  in  order  to  cause  the  steam  and  water  to  ascend 
spirally,  whilst  the  top  of  the  internal  tube  was  formed  with  a 
tapering  or  extended  mouth  so  as  to  collect  the  revolving 
current  of  water  and  direct  it  into  the  tube.  In  the  illustration, 
which  shows  the  boiler  as  tested  at  the  International  Exhibition 
at  Philadelphia  in  1876,  the  form  of  the  boxes  or  tube-heads 
was  altered,  as  well  as  that  of  the  internal  circulating  tubes. 

In  the  boilers  of  C.  M.  Barker,  1869  (No.  1228),  and  of 
Rogers  and  Black,  the  latter  of  which  was  also  tried  at  Phila- 
delphia in  1876,  and  is  illustrated  in  D.  K.  Clark's  "  Steam 

Engine/'  &c.,  Vol.  i.,  p.  255, 
vertical  water  -  tubes  were 
combined  with  a  cylin- 
drical shell,  in  the  one  case 
inside  and  in  the  other  out- 
side of  the  larger  vertical 
cylinder. 

Finn  i  nick     Boiler.  --  The 
Firminich    boiler    was    also 


introduced  in  America,  and 
was  among  the  boilers 
tested  in  1876  at  Philadel- 
phia. 

Fig.  244  shows  its  form. 
It  was  composed  of  vertical 
water  tubes,  two  rows  of 
which  were  connected  top 
and  bottom  to  cylindrical 
chambers  running  from  front 
to  back  of  the  boiler. 

Fryer's  Boiler. — A.  Fryer  patented  in  1874  (No.  1774)  a  pecu- 
liar design  of  vertical  tube  boiler  which  is  shown  in  the  illustra- 
tion, Fig.  245.  It  had  three  horizontal  chambers  above  and  four 
below,  the  centre  one  of  the  three  above  and  the  two  inner  ones 
below  being  of  larger  diameter  than  the  others.  Several  rows 
of  small  water-tubes  connected  the  upper  and  lower  chambers, 
some  of  them  being  bent  at  one  end  and  the  others  being 
straight,  and  large  downcomer  passages  were  also  constructed 
between  the  three  larger  chambers.  After  the  success  of  some 
of  the  three-chamber  boilers,  to  be  subsequently  described,  this 


THE  MODERN  STEAM  BOILER. 


441 


design  was  considerably  altered,  and  in  the  discussion  of  a  paper 
on  "  Torpedo  Boat  Destroyers,"  in  the  Institution  of  Civil  Engi- 
neers (Min.  Proc.  Inst.  C.E.,  Vol.  cxxii.,  p.  81),  Mr.  D.  Halpin 
put  forward  Fig.  246  as  a  representation  of  the  boiler  invented 
by  Fryer.  The  contrast  between  the  two  is,  however,  too 


FIG.  24.4. 

glaring  to  pass  without  notice  ;  but  this  is  not  the  only  design 
which  has  been  subjected  to  some  alteration  in  order  to  bring  it 
into  conformity  with  more  modern  ideas. 

Rowan's  Boiler. — In  1876  (No.  4430)  the  author  of  this  work 
patented,  as  a  development  from  the  Rowan  and  Horton  designs 


442 


THE  PRACTICAL  PHYSICS  OF 


FIG.   245. 


THE  MODERN  STEAM  BOILER. 


443 


already  referred  to,  and  with  a  special  view  to  the  requirements  of 
vessels  of  the  Navy,  a  toiler  composed  of  three  cylindrical  cham- 
bers, arranged  horizontally  one  on  each  side  of  the  fireplace  and 
one  above,  so  that  lines  drawn  through  their  centres  would  form 
a  triangle,  with  vertical  water-tubes  slightly  inclined  and  having 
their  ends  bent  to  enter  the  cylindrical  chambers  radially.  This 
boiler  is  illustrated  in  Fig.  247  and  Figs.  52  and  53  (Chap.  III.), 


FIG.    246. 


and  it  was  undoubtedly  the  first  of  a  type  which  in  more  recent 
years  has  become  widely  used,  the  three-chamber  boilers  of 
Yarrow,  Thornycroft,  Normand,  Blechynden,  Reed,  Fleming  and 
Ferguson,  and  many  others  being  modelled  on  the  same  type  with 
some  differences  in  the  shape  given  to  the  water-tubes  joining 
the  three  chambers.  Distinct  downcomer  tubes  were  at  first 
common  to  all  these  boilers,  but  latterly  Mr.  Yarrow  discarded 
these  and  preferred  to  utilise  the  outer  rows  of  small  water 
tubes  for  the  downward  currents  of  water. 


444 


THE  PRACTICAL  PHYSICS  OF 


FIG.    247. 


Thornycroft' s  Boiler. — J.  I.  Thornycroft's  three-chamber  boiler 
("  Speedy  type")  seems  to  have  been  patented  in  1885  (No.  1404), 
although  it  was  not  brought  prominently  forward  until  some  years 
later.  It  is  shown  in  Figs.  248  and  249,  and  has  been  frequently 
described  in  his  own  and  other  papers.  See  especially  Min.  Proc. 
Inst.  C.E.,  Vol.  xcix.,  p.  41,  and  Trans.  Inst.  N.A.,  1889.  The  tubes 
are  bent  so  as  to  enter  the  steam  chamber  on  the  upper  side  above 
the  water  level.  Mr.  Thornycroft  has  also  introduced  another  form 
of  water-tube  boiler,  in  which  there  are  only  two  main  horizontal 
chambers,  and  the  water-tubes  are  connected  to  these  in  such  a 
way  that  the  outline  of  the  boiler  somewhat  resembles  that  of  a 
peg-top.  This  is  known  as  the  "  Daring  type,"  and  is  illustrated 
in  Fig.  250.  Descriptions  of  it  and  its  work  \vill  be  found  in 
comparatively  recent  papers  by  Mr.  Thornycroft  and  by  Mr.  J.  T. 
Milton  (Inst.  C.E.,  Vol.  cxxxvii.  and  Trans.  Inst.  N.A.).  This  form 
was  patented  in  1890  (No.  17809). 

White's  Boiler. — Another  three-chamber  boiler  was  patented 
by  J.  L.  and  H.  S.  White  in  1889  (No.  6934),  and  1893  (No.  18076). 


THE  MODERN  STEAM  BOILER. 


445 


FIG.   248. 


FIG.   249. 


FIG.   250. 


446 


THE  PRACTICAL  PHYSICS  OF 


FIG.   251. 


THE  MODERN  STEAM  BOILER. 


447 


In  addition  to  the  nearly  straight  tubes  connecting  the  two  lower 
with  the  upper  chambers,  it  had  a  number  of  tubes  bent  in  cork- 
screw form  rilling  up  the  combustion  space,  and  thus  adding 
considerably  to  the  amount  of  heating  surface. 

Fig.  251  illustrates  this  boiler,  which  was  described  by  Mr. 
J.  T.  Milton  in  Trans.  Inst.  N.A.,  Vol.  xxxv.,  1894,  page  303. 

Another  form  of  the  three-chamber  boiler  is   made  by  the 


FIG.    253. 

Liquid  Fuel  Engineering  Co.,  of  East  Cowes,  Isle  of  Wight, 
and  is  illustrated  by  Fig.  252.  In  this  form  the  small  tubes 
between  the  two  lower  and  the  upper  chambers  are  crossed,  as 
will  be  seen,  and  enter  the  steam  chamber  on  the  upper  side. 

Other  three-chamber  forms  are  those  of  H.  A.  House  and  R. 
Symon,  1893  (No.  17224)  ;  J.  W.  Davis,  1893  (No.  17473)  ;  G.  F. 
Des  Vignes,  1893  (No.  18419)  ;  B.  H.  Thwaite  and  J.  B.  Fur- 
neaux,  1893  (No.  20414)  ;  R.  Schulz,  1894  (No.  1297)  ;  P.  Smit 


448  THE  PRACTICAL  PHYSICS  OF 

1894  (No.  7793)  ;  T.  Herald,  1894  (No.  7794)  ;  SirC.  Ross,  1894 
(No.  8472)  ;  O.  D.  Orvis,  1895  (No.  5740)  ;  J.  Patterson  and  J.  A. 
Sandilands,   1895  (No.    10441)  ;  P.   Bentzene  and  C.   F.   Olsen, 

1895  (No.    12754)  I    E.    Lagosse,    1895    (No.    16013)  ;    H.    Du 


OOQ.OOOO-O 
o    o    o    o    o    o    o  / 


-A-  -0» ^-^  — 


FIG.   254. 


Temple,  1895  (No.  17200)  ;  H.  Mclntyre,  1896  (No.  4352)  ;  J.  P. 
Hall,  1896  (No.  10774)  J  Du  Temple,  1897  (No.  11570)  J  Hills 
and  Young,  1897  (No.  19876),  &c. 

Yarrow's    Boiler. — Mr.    Yarrow's    three-chamber    boiler    was 
patented  in  1889  (No.  17958).     In  it  the  two  lower  chambers 


THE  MODERN  STEAM  BOILER. 


449 


are  made  of  approximately  semi-circular  form,  the  flat  surface 
enabling  all  the  water-tubes  to  be  inserted  without  a  bend. 

Fig.  253  illustrates  this  boiler,  of  which  descriptions  will  be 
found  in  Trans.  Inst.  N.A.,  1893,  in  Cassier's  Magazine  for  August 
1897,  and  in  several  other  technical  publications. 

Du  Temple  Boiler. — The  boiler  of  M.  Du  Temple,  as  now 
known  and  as  patented  in  Britain  in  1891  (No.  518),  is  another 


FIG.   255. 

modification  of  the  three-chamber  design,  the  two  lower  cham- 
bers, however,  being  in  this  case  of  square  shape,  and  the  tubes 
having  a  more  sinuous  form  than  in  most  of  the  other  modifica- 
tions. 

This  boiler  is  illustrated  in  Fig.  254,  but  according  to  M. 
Bertin  ("  Marine  Boilers,"  pp.  297-302),  the  tendency  of  recent 
improvement  in  this  boiler  has  been  towards  a  less  sinuous 
form  of  water  tubes  and  a  greater  approximation  to  the  form 

Q 


450 


THE  PRACTICAL  PHYSICS  OF 


of  the  Normand  boiler.     This   is  shown  in   his  British   patent 

of  1895. 

An  older  design,  associated  in  this  country  with  the  name  of 

M.  Du  Temple,  is  shown  in  Fig.  255,  and  is  seen  to  combine  the 

steam  chamber  at  the  upper   ends  of  the  bent  water-tubes  with 

a   single   water   chamber   of  square    shape  at  the  lower  ends. 

There   is  an   external  downcomer  tube,  as  in  the  case  of  the 

other  Du  Temple  boilers. 

This   form   \vas    patented    in    Britain    in    1880    (No.    2554). 

Further  patents  are  dated  1893  (Nos.  7923,  8251)  and  1895  (No. 

17200). 

Coivles'  Boiler.— The  boiler  of 
W.  Cowles  was  introduced  in 
America,  and  was  patented  in 
Britain  in  1889  (No-  Il6l)«  ^ 
also  adheres  to  the  three-chamber 
type,  but  has  a  more  elaborate 
arrangement  of  bent  water-tubes 
than  the  other  examples  of  this 
type.  This  will  best  be  under- 
stood from  the  drawing.  Fig.  256 
represents  this  boiler  as  described 
by  Mr.  W.  M.  McFarland  at  the 
International  Engineering  Con- 
gress, Chicago,  in  1893.  It  will 
be  noticed  that  for  a  short  length 
the  back  portion  of  the  steam 
drum  is  reduced  in  diameter, 
at  which  part  the  water-tubes 

branch  out  from  nearly  the  \vhole  circumference.     These  tubes 

are   made  to  fill  the  back  space  of  the  combustion  chamber, 

the  increased  number  of  them  enabling  them  to  be  laid  fairly 

close  together.     Other  tubes    attached    to  box   branches    form 

the  side  walls  of  the  combustion  space. 

Andrews'  Boiler. — In  1892  (No.   13185)  J.  Andrews  patented 

another  example  of  the  three-chamber  type,  which  is  shown  in 

Fig.  257. 

It   differs   from   that   of    Yarrow    and     others   in    the   form 

adopted  for  the  chambers.     The  form  of  the  upper  chamber 

necessitates  an  additional  steam  drum. 


FIG.   256. 


THE  MODERN  STEAM  BOILER.  451 

Fleming  and  Ferguson's  Boiler. — The  boiler  known  as  Fleming 
and  Ferguson's  "  Clyde  "  boiler  was  patented  by  P.  Ferguson 
and  W.  Fleming  in  1892  (No.  24141).  It  is  illustrated  in  Fig. 
258,  which  shows  that  in  this  case  the  three  chambers  are  con- 
nected by  water-tubes,  which  are  all  bent  throughout  their  entire 


length  to  some  arc   of  a  circle.     Otherwise  there  is  no  striking 
difference  between  this  and  other  forms  of  the  same  type. 

Norniand  Boiler. — This  type  was  introduced  in  France  by  M. 
Norrnand,  who  first  of  all  improved  the  Du  Temple  boiler,  until 
it  but  slightly  differentiates  from  some  other  forms,  and  later 
brought  out  the  boiler  which  is  associated  with  his  own  name. 


FIG.  258. 


The  stages  of  these  interesting  developments  are  traced  in  M. 
Bertin's  work  on   Marine    Boilers  (Bertin    and  Robertson,  pp. 


The  Normand  boiler  is  illustrated  in  Fig.  259,  from  which  it 
will  be  seen  that  in  the  form  of  the  water-tubes  it  resembles  the 


452 


THE  PRACTICAL  PHYSICS  OF 


original  Rowan  three- chamber  boiler  more  than  any  of  the 
others.  The  Normand-Sigaudy  boiler,  1895  (No.  4975)  consists 
of  two  such  boilers  joined  back  to  back. 

The  Normand  boiler  was  patented  in  Britain  in  1894  (Nos. 
2315,  25004). 


FIG.   259. 

Blechynden  Boiler.  The  late  Mr.  Blechynden  patented  in 
1893  (Nos.  18311,  22949),  1895  (Nos.  9517,  17221)  the  form  of 
three-chamber  boiler  with  which  his  name  is  associated.  It  is 
shown  in  Fig.  260,  and  its  peculiarity  is  seen  to  consist  in  having 
the  steam  chamber  larger  than  usual,  and  a  slight  bend  in  the 
water-tubes  so  that  any  of  these  can  be  withdrawn  or  replaced 


THE  MODERN  STEAM  BOILER. 


453 


from  hand  holes  arranged  in  the  top  of  the  steam  chamber. 
Mr.  Blechynden's  boiler  has,  like  several  of  the  other  modifica- 
tions of  this  type,  been  introduced  into  the  smaller  vessels  of 
H.M.  Navy.  It  is  now  constructed  by  Messrs.  Henry  Watson 
and  Sons,  of  Newcastle. 

Reed's  Boiler. — The  only  other  marine  boiler  of  this  type,  of 
importance,  is  the  one  introduced  by  Mr.  J.  W.  Reed,  in  1893 
(Nos.  22982,  24124),  1896  (No.  4654),  and  constructed  by  Palmer's 
Shipbuilding  Company. 

It  is  illustrated  in  Fig.  261.  In  it  the  three  chambers 
are  all  cylindrical  in  form,  and  the  bend  of  the  water-tubes 
resembles  the  form  adopted  in  the  Du  Temple  -  Normand 
boilers  of  the  "  Mangini."  The  two  rows  of  tubes  over  the  fire 
are,  however,  in  the  Reed  Boiler,  zig-zagged  to  give  increased 
heating  surface,  and  down- 
comer  tubes  are  supplied  at 
each  end  of  the  horizontal 
chambers. 

Maxim's  Boiler. — The  varia- 
tions in  form  of  water-tubes 
adopted  in  this  type  is  further 
illustrated  in  the  boiler  con- 
structed by  Mr.  H.  S.  Maxim 
for  his  flying-machine.  This 
is  shown  in  Fig.  262. 

MumfonVs  Boiler. — A  modification  of  this  type  was  introduced 
by  Mr.  A.  G.  Mumford  of  Colchester,  in  1893,  for  small  boilers, 
from  which  he  developed  another  arrangement  suitable  for 
larger  powers.  In  this  case,  as  is  shown  in  Fig.  263,  the  three 
chambers  are  attached  by  branch  pipes  to  boxes  which  contain 
clusters  of  small  bent  water-tubes.  The  intermediate  joints  give 
undoubted  facility  for  the  removal  and  repair  of  any  of  the 
individual  clusters,  and  in  the  erection  of  a  boiler  on  board  ship 
there  is  no  riveting  or  tube  expanding  required.  This  consti- 
tutes the  special  advantage  possessed  by  this  design.  Mr. 
Mumford's  patents  are  dated,  1893  (No.  8729),  1895  (Nos. 
8043  and  15549),  J897  (No.  8498),  1898  (No.  19008),  1899  (No. 
9898). 

This  boiler  has  also  been  introduced  for  trial  in  H.M.  Navy. 

Another    modification    of    the     three-chamber     design    was 


KIG.   2fiO. 


454 


THE  PRACTICAL  PHYSICS  OF 


THE  MODERN  STEAM  BOILER. 


455 


456 


THE  PRACTICAL  PHYSICS  OF 


proposed  by  C.  S.  Galloway  in  1894  (No.  19913),  and  a  further 
one  by  Mr.  James  Weir  later. 

Weir  Boiler. — Mr.  Weir  patented  in  1894  (No.  3724)  a  boiler  with 
two  horizontal  drums  connected  by  a  number  of  small  water- 
tubes  ;  also  a  central  vertical  chamber  and  small  tubes  curving  from 
the  top  to  near  the  bottom,  and  other  forms.  In  subsequent 
patents,  No.  4995  and  28961  (1896),  No.  9177  (1897)  and  No. 
12308  (1898),  he  developed  various  designs  with  the  object  of 
forming,  by  means  of  bent  water-tubes,  a  combustion  space  for 
secondary  combustion  of  the  hot  gases  which  are  cooled  often 


K1G.   263. 

to  the  point  of  extinguishing  flame  by  their  first  contact  with 
the  heating  surface.  As  shown  by  his  paper,  read  before  the 
Institute  of  Engineers  and  Shipbuilders  in  Scotland,  Vol.  xlii. 
pp.  12 — 40  and  plate  2,  Mr.  Weir  finally  fixed  upon  the  three- 
chamber  form  as  the  most  suitable  for  carrying  out  his  plan. 

WTith  regard  to  all  the  forms  of  this  three-chamber  type,  it  is 
apparent  that  the  more  the  water-tubes  are  bent  or  twisted  into 
fantastic  shapes,  the  more  is  the  advantage  of  having  straight 
vertical  tubes  lost,  and  facility  of  examination  is  also  lost  in 
proportion.1 

1  See  The  Engineer.     November  21,  1890,  p.  408. 


THE  MODERN  STEAM  BOILER. 


457 


Mosher' s  Boiler. — The  boiler  of  C.  D.  Mosher,  introduced  in 
America  in  1880,  but  patented  in  Britain  in  1892  (No.  1725),  has 
only  two  chambers  to  each  group  of  tubes,  but  usually  four 
chambers  are  connected  to  form  a  boiler  as  is  shown  in  Fig.  264. 
The  arrangement  of  the  water-tubes  is  in  some  respects  similar 
to  that  of  the  Cowles  boiler,  but  in  delivering  their  contents 
above  the  water-line  in  the  top  chamber,  it  resembles  the 


FIG.   264. 

Thornycroft  boilers.  Further  designs  were  patented  by  Mosher 
in  1894  (Nos.  17285  and  17286). 

Seabury,  Symon-Honse,  and  Gurncy  Boilers. — Seabury's  Boiler 
of  1892  (American  patent  No.  497432)  has  also  two  chambers, 
but  the  water-tubes  are  bent  outwards  on  each  side  to  embrace 
the  fire,  which  is  placed  between  the  two  horizontal  chambers- 
see  Fig.  265. 

Of  a  similar  design  is  the  Symon- House  boiler  (illustrated  in 


458 


THE  PRACTICAL  PHYSICS  OF 


Berlin  and  Robertson's  Marine  Boilers,  page  324),  which  is 
almost  the  counterpart  of  the  boiler  patented  by  L.  Mills  and 
W.  Clark  in  1878  (No.  3865),  whilst  both  of  these  boilers  recall 

the  original  boiler  of  Goldsworthy 
Gurney  in  1825  (No.  5270),  which  is 
illustrated  in  Fig.  266,  and  Craddock's 
Boiler  of  1857  (Nos.  931  and  1162). 

A  number  of  Patents  for  vertical  or 
vertically  inclined  water-tube  boilers 
were  taken  out  during  the  years  from 
1880  to  1896,  few  of  which  require 
any  particular  notice.  Of  these  the 
names  of  the  following  are  sufficient : — 
Ballian,  1880  (No.  4662),  Stevenson, 
1883  (No.  5907),  Lake,  1884  (No-  X42o)> 
Leutner,  1884  (No.  12013),  Allen,  1886 
(No.  10780),  Seabury,  1889  (No.  4279), 
FIG.  265.  Haurez,  1889  (No.  10056),  King  and 

Clark,   1889   (No.  11735),  Van  Steen- 

bergh,  1890  (No.  3020),  Drory,  1892  (No.  15069),  W.  H.  Wat- 
kinson,  1896  (No.  15721)  (see  page  506). 

Ward's   Boiler.— In    1888    (No.    11617),    Mr.  Chas.   Ward  of 
Charlestown,    U.S.A.,  patented   in    Britain    a    boiler    composed 


FIG.  266. 


principally  of  vertical  water-tubes,  which  he  had  introduced  in 
America.  This  is  illustrated  in  Fig.  267,  and  is  usually  known  as 
Ward's  Torpedo-boat  Boiler.  This  boiler  is  circular  on  plan, 


THE  MODERN  STEAM  BOILER. 


459 


the  casing  being  cylindrical.  At  the  bottom,  and  supported  by 
the  ash-pit,  is  a  cast  steel  circular  tube  of  about  4^  inches 
diameter,  forming  a  circle  of  some  three  feet.  Small  branches 
or  seats  are  formed  on  the  top  side  of  this  ring  into  which 
vertical  water-tubes  are  fitted  to  form  two  rows,  placed  zigzag 
on  plan,  surrounding  the  fire.  At  the  top  these  tubes  are  bent 
to  a  quarter  of  a  circle  to  enter  radially  the  shell  of  a  vertical 
cylindrical  steam  drum. 
From  the  bottom  of  this 
steam  drum  three  rows  of 
pendant  tubes  are  fixed, so 
that  they  hang  slightly  in- 
clined towards  the  vertical 
tubes  outside.  The  lower 
ends  of  these  hanging  tubes 
are  closed  by  caps,  and  each 
tube  has  an  internal  tube  for 
water  circulation.  The  en- 
closing casing  is  of  sheet 
iron,  double,  with  asbestos 
board  between  the  two 
sheets. 

Stirling's  Boiler.  --  The 
boiler  known  as  tt^e  Stirling 
Water-tube  Boiler  was 
patented  in  this  country  by 
A.  Stirling  in  1889  (No. 
11413),  further  patents  being 
taken  out  in  1892  (No.  13614) 
and  1895  (No.  13733)-  !t  is 
represented  in  Fig.  268,  and 
is  composed  of  vertically 
inclined  water  -  tubes  set 
radially  into  horizontal  chambers  at  each  end  in  the  same 
manner  as  in  the  Rowan  and  Horton  boiler  of  1869. 

The  Stirling  boiler  was  introduced  in  America  and  has  been 
used  hitherto  only  for  land  or  stationary  purposes. 

Similar  designs  have  been  patented  in  this  country  by  J.  Pier- 
point  in  1892  (No.  7039),  and  in  America  by  H.  S.  Pell  on  22nd 
December,  1893. 


FIG.   267. 


460 


THE  PRACTICAL  PHYSICS  OF 


Particulars  of  the  Stirling  water-tube  boilers  used  at  the 
Chicago  Exhibition,  will  be  found  in  The  Engineer,  of  August 
4th,  1893,  p.  no.  As  now  made  by  the  Stirling  Boiler  Co.,  Ltd., 


FIG.   268. 


of  Edinburgh  and  Motherwell,  this  boiler  as  adapted  lor  use 
on  land  has  been  modifieed.  Particulars  of  its  latest  form 
will  be  found  in  The  Engineering  Times'  Record  of  the  Machinery 
in  the  Glasgow  International  Exhibition,  in  Feilden's  Magazine 


THE  MODERN  STEAM  BOILER. 


461 


for  1901  and  elsewhere.  See  Fig.  269.  A  marine  boiler 
projected  by  this  Company  is  in  course  of  development 
also. 

JardinJs  Boiler. — A  boiler  on  somewhat  similar  lines  was 
patented  by  John  Jardine  in  1896  (No.  5702),  and  is  known  as 
the  "Glasgow  Patent  Water-tube  Boiler." 

In  this  boiler  the  vertical  water-tubes  are  connected  with  two 
water  drums  behind  the  furnace,  in  the  same  way  as  in  the 


FIG.   269. 


Stirling  boiler,  but,  instead  of  its  three  steam  drums  above  placed 
parallel  with  the  water  drum,  in  the  "  Glasgow  "  boiler  there  are 
two  horizontal  steam  drums  placed  at  right  angles  to  the  axis  of 
the  water  drums  below. 

Fig.  270  illustrates  this  boiler,  which  is  manufactured  by 
Messrs.  Duncan  Stewart  and  Co.,  Ltd.,  of  Glasgow. 

Peterson's  Boiler. — The  Peter  son- Macdonald  boiler  is  allied  to 
the  three  chamber  type,  but  has  some  distinctive  features.  The 
vertically-inclined  tubes  are  connected  in  groups  or  "  nests  "  of 


462 


THE  PRACTICAL  PHYSICS  OF 


THE  MODERN  STEAM  BOILER. 


463 


nine  tubes  to  a  steel  box  at  each  end,  and  these  boxes  are  con- 
nected to  the  steam  drum  at  the  top  end  of  the  tubes,  and  to 
branches  from  stand  pipes  at  the  other  end.  These  stand  pipes 


HO.   271. 


connect  at  each  side  of  the  fire-place  to  small  water  drums  placed 
alongside  the  ashpit. 

Fig.  271  shows  this  boiler  as  so  arranged. 


464 


THE  PRACTICAL  PHYSICS  OF 


FIG.  272. 


THE  MODERN  STEAM  BOILER 


465 


FIG.  273 


466 


THE  PRACTICAL  PHYSICS  OF 


Another  form  arranged  as  a  horizontally  inclined  boiler  is 
shown  in  G.  Halliday's  book  on  "  Steam  Boilers,"  p.  334,  from 
which  Fig.  272  is  taken. 

Experience  in  the  manufacture  of  this  boiler  as  originally 
designed  is  said  to  have  shown  that  some  alteration  was 
desirable  in  consequence  of  difficulty  in  readily  altering 
the  angles  of  the  tubes  for  any  small  variation  of  width 
of  fire  -  grate.  Accordingly,  the  horizontal  form  was  pro- 
posed and  a  later  improvement  upon  that,  which  has  been 
developed  by  Messrs.  Clarke,  Chapman  and  Co.,  Ltd.,  and 
adopted  by  the  Peterson  Water-tube  Boiler  Co.,  is  shown  in 
Fig.  273. 

In  addition  to  a  new  arrangement  of  the  nests  of  tubes,  or  of 
the  "  compound  tubes,"  as  they  are  called,  an  economiser  and 

a  primary  heater,  which  latter 
consists  of  a  serpentine  coil  of 
tube  of  2§  ins.  outside  diameter, 
arranged  on  the  two  wings  of 
the  boiler,  are  added.  Feed 
regulating  valves  are  also  used, 
so  that  the  water  may  be  made 
to  traverse  the  heater  until 
natural  circulation  commences. 
The  water,  heated  first  in  the 
primary  heater  and  then  in  the 
economiser,  is  delivered  into 
the  steam  drum. 

The  patents  for  the  Peterson  boiler  are  dated,  1891  (No- 
18698),  1893  (No.  23577),  1894  (No.  23346),  1895  (No.  17722), 
and  the  improved  form  1899  (No.  12343). 

Stevenson's  Boiler. — G.  Stevenson,  in  1883  (No.  5907),  patented 
an  arrangement  of  vertical  and  vertically  inclined  water-tubes 
fastened  to  the  outside  of  a  cylindrical  water  chamber.  The 
tubes  were  closed  at  the  end  and  each  contained  a  circulating 
tube. 

Yarrow's  Boiler. — A  more  workable  design  having  some  ideas 
in  common  with  Stevenson's,  was  patented  by  A.  F.  Yarrow  in 
1893  (No.  24690).  This  consisted  of  a  cylindrical  water  and 
steam  drum,  from  which  a  number  of  water  tubes  depended 
obliquely,  so  as  to  spread  on  each  side  of  the  fire,  see  Fig.  274. 


FIG.   274.. 


THE  MODERN  STEAM  BOILER. 


467 


H  H  2 


468 


THE  PRACTICAL  PHYSICS  OF 


These  tubes  were  closed  at  their  lower  end,  and  each  contained 
a  circulating  tube  or  partition. 

Thorn's  Boiler. — Considerable  improvement  in  this  design  was 
made  by  John  Thorn  in  his  patent  of  1896  (No.  2793).  This  boiler 
is  illustrated  in  Figs.  275  and  276,  from  which  it  will  be  seen  that 
although  it  has,  like  Yarrow's,  tubes,  closed  at  one  end,  depend- 
ing obliquely  from  a  cylindrical  steam  and  water  chamber,  yet 
by  the  ingenious  plan  of  reducing  the  diameter  of  some  of  these 


FIG.   276. 

tubes  where  they  enter  the  tube  plate,  Mr.  Thorn  was  enabled  to 
arrange  them  in  contact  to  form  water  walls,  dividing  the  furnace 
space  for  two  fires  and  constructing  combustion  chambers  and 
flues,  almost  at  will.  This  boiler  has  been  successfully  intro- 
duced by  Mr.  Thorn,  for  use  in  both  marine  and  land  work. 

Phillips'  Boiler. — Another  boiler  of  the  same  class  has  been 
proposed  by  H.  F.  Phillips. 

The  earlier  form  of  this  boiler,  which  does  not  seem  to  have 
been  patented,  is  shown  in  Fig.  277,  from  G.  Halliday's  "  Steam 
Boilers  "  (pp.  336,  337).  In  this  form,  the  tubes  were  spread  out 


THE  MODERN  STEAM  BOILER. 


469 


IRCULATING 
TUBE 


to  form  five  rows  of  equal  length, 
on  each  side  of  a  single  fire-place. 
The  outer  tubes  were  contracted 
at  their  lower  ends  to  receive  a 
plug  containing  a  small  blow-off 
valve,  and  the  inner  tubes  rested  on 
the  plug  and  had  holes  cut  in  their 
sides  and  on  the  bottom  edge  to  per- 
mit of  water  circulation  (Fig.  277A). 
In  the  later  form  of  the  Phillips' 
boiler,  shown  in  Fig.  278,  which 
was  patented  in  1898  (No.  8814), 
the  pendent  tubes  are  arranged 
to  form  spaces  for  five  fire-places 

with  a  double  row  of  tubes  between  each  of  them,  and  on  the 
two  outside  flanks  of  the  boiler,  seven  rows  of  tubes.     The  idea 


CASING 


Kit;.  277. 


470 


THE  PRACTICAL  PHYSICS  OF 


of  this  arrangement  is  to  have  as  large  a  proportion  of  the 
heating  surface  as  possible  under  the  influence  of  the  radiant 
heat  of  the  fires.  There  is,  of  course,  perfect  freedom  of 
expansion  and  contraction  in  the  tubes  of  this  class  of  boiler, 
so  that  it  avoids  many  strains  in  working.  This  form  of  the 
Phillips  boiler  is  stated  to  have  performed  well  on  test,  although 


FIG.   278. 

the  rate  of  evaporation  per  square  foot  of  heating  surface  was 
8*15  Ibs.  of  water  at  250  Ibs.  per  square  inch  pressure  of  steam, 
and  8' i  Ibs.  water  per  Ib.  of  coal  from  and  at  212°  F.,  which 
cannot  be  called  a  high  rate  for  a  water-tube  boiler. 

Haythorn    Boiler, — The    Haythorn    boiler    was    patented    in 
1894  (Nos.  9570  and  12846).      In   it  the  water-tubes  are  vertical 


THE  MODERN  STEAM  BOILER. 


471 


at  starting  from  the  lowest  point,  and,  after  following  an  easy 
curve,  finish  off  at  an  incline  above  the  horizontal.  The 
tubes  are  connected  to  headers  at  each  end  ;  the  lower  headers 
being  laid  side  by  side  behind  the  fire-grate,  in  the  line  of 
fire  bars,  and  the  upper  headers  at  the  boiler  front  inside 


FIG.   279. 

the  casing.  Each  pair  of  headers  (the  upper  and  lower) 
provides  for  a  double  row  of  water-tubes,  and  either  one  or  two 
larger  tubes  which  are  on  the  outside  of  all  and  act  as  down- 
comers.  The  portion  of  the  front  headers  to  which  the 
downcomer  tubes  are  attached  is  enlarged  to  form  a  separate 
passage  for  the  water,  the  upward  steam  passage  being  in 


472  THE  PRACTICAL  PHYSICS  OF 

front.  A  cylindrical  drum  is  placed  across  the  boiler  front, 
and  is  connected  by  flanges  to  the  tops  of  the  front  headers.  As 
first  made,  the  Hay  thorn  boiler  was  as  illustrated  in  Engineering 
Vol.  lx.,  page  680,  whilst  in  Fig.  279  the  latest  form  is 
shown  as  arranged  for  marine  use.  The  water  level  is  at 
about  the  centre  of  the  cylindrical  drum,  into  which  the 
feed  is  delivered,  whilst  a  door  for  clearing  out  mud  and 
a  blow-off  cock  are  provided  at  the  lowest  point  of  the  back 
headers  below  the  downcomers.  '  Formerly  fire  bricks  were 
used  as  baffle  plates,  but  in  the  recent  form  these  are  abolished, 
and  the  tubes  are  laid  together  where  wanted  to  form  water 
walls. 

The  boilers  patented  by  Galloway  and  Wilson,  1861  (No. 
1948),  William  Inglis,  1862  (No.  3307),  and  J.  T.  Romminger, 
1865  (No.  771)  may  be  classed  with  vertical  water-tube  boilers, 
as  also  the  designs  patented  by  the  author  in  1894  (No. 
8170).  Of  modifications  of  the  vertical  design  the  one  proposed 
by  Shepherd  in  1873  (No.  1849),  and  1877  (No.  1699)  is, 
perhaps,  the  only  one  requiring  notice. 

Shepherd's  Boiler. — This  boiler  is  illustrated  by  Fig.  280, 
and  was  composed  of  vertical  vessels,  partly  cylindrical  and 
partly  conical  in  shape,  set  in  two  or  three  rows,  with  horizontal 
cylinders  or  large  tubes  below,  into  which  the  feed  entered.  A 
certain  portion  of  the  cylindrical  upper  part  of  the  vertical 
vessels  was  used  as  steam  space,  and  a  steam  pipe  connected  all 
these  vessels  by  vertical  branches  from  their  domed  tops 
at  the  centre. 

Coil  Boilers. — At  an  early  date  various  forms  of  coiled  tube 
boilers  were  proposed,  probably  because  a  considerable  area 
of  heating  surface,  without  the  trouble  of  making  many 
joints,  could  be  obtained  within  a  small  space.  Fitch  and  Voight 
and  James  Rumsey  were  the  first  to  bring  forward  this  design, 
and  they  were  soon  followed  by  Seaward  and  Paul,  who 
used  forms  of  coils  in  the  construction  of  their  "  flash  "  boilers. 
(See  pp.  361 — 362  ante). 

Gurnets  Boiler. — Goldsworthy  Gurney  in  1825  (No.  5270) 
and  in  1827  (No.  5554)  patented  two  forms  of  water-tube 
boilers,  the  first  having  been  the  one  already  referred  to 
(p.  458),  whilst  the  second  was  more  properly  a  coil  boiler. 
It  has  been  represented  by  Fig.  281,  which  was  the  form 


THE  MODERN  STEAM  BOILER.  473 

ultimately  adopted  for  this  boiler  in  connection  with  the  historic 


introduction    of   steam   automobilism   in    the    early  part  of  the 
1 9th    century.       An    earlier   form   of    this    boiler    is    shown   in 


474 


THE  PRACTICAL  PHYSICS  OF 


Fig.  282,  which  is  evidently  less  suitable  for  the  confined  space 
of  a  motor  vehicle. 


HA  LF'       PLAN 


FIG.   28l. 


FIG.   282. 


J.  Rawe  and  J.  Boase  followed  in  1830  (No.  5956)  with  a 
boiler  composed  of  a  series  of  helical  coils  of  tubes,  but  of 
its  use  we  have  no  record. 


THE  MODERN  STEAM  BOILER. 


475 


Dance  and  Field's  Boiler.— The  boiler  of  Dance  and  Field, 
1833  (No.  6465)7  was,  however,  introduced  in  motor-car 
work,  and  seems  to  have  done  its  work  fairly  well.  It  is  shown 
in  Fig.  283  as  constructed  by  Messrs.  Maudslay  and  Field  for 


FIG.   283. 


the   steam    motor    which   ran   from    London    to  Reading  and 
back,  towing  an  omnibus  full  of  passengers. 

One  of  W.  H.  James'  patents,  viz.,  the  one  for  1855 
(No.  1998)  was  for  a  coiled  tube  boiler,  but  excepting  the 
Belleville  designs  of  1852  and  1856  (already  mentioned) 


THE  PRACTICAL  PHYSICS  OF 


there  was  no  coil  boiler  of  importance  brought  out  for 
many  years.  The  following  are  the  principal  patents  for 
coil  boilers  :— W.  Morgan,  1838  (No.  7848),  J.  T.  Beale, 
1840  (No.  8564),  Belleville,  1852  and  1856,  W.  E.  Newton, 

1854  (No.   1361),  J.  H.  Johnson,  1855   (No.  223),   M.   F.  Isoard, 

1855  (No.     1637),.   J.    A.    Hopkinson,    1858    (No.     2558),    G. 
Scott,    1858    (No.    565)   and    1859  (No.    2317),  S.   S.  Bateson, 
1860  (No.  480). 

Matheson's   Boiler. — Some  of    these    inventors    make    use    of 
spiral  coils,  but  the  most  simple  application  of  this  device  is 

found  in  the  boiler  patented 
by  H.  Matheson  in  1861 
(No.  94),  which  is  repre- 
sented in  Fig.  284,  as  illus- 
trated by  Mr.  Thornycroft 
in  Min.  Pro.  Inst.,  C.E. 
Vol.  xcix.  Plate  i.  Fig.  7. 
Although  this  boiler  appa- 
rently provides  for  con- 
tinuous and  systematic  cir- 
culation of  the  water  in  one 
direction,  the  danger  of  this 
and  of  all  similar  arrange- 
ments is  that  a  rapid  gene- 
ration of  steam  in  the  water 
supply  pipe  to  the  coil  (or 
the  lowest  branch  of  the 
coil),  which  is  exposed  to 
the  direct  heat  of  the  fire, 
would  probably  cause  an 
interruption  of  the  circulation  on  account  of  that  steam  seeking 
the  readiest  means  of  escape,  some  of  it  preferring  to  go  up 
through  the  water  chamber  rather  than  by  the  longer  and  more 
tortuous  road  provided  by  the  spiral.  Such  action  has  happened 
in  several  water-tube  boilers  of  different  designs,  and  the 
immediate  overheating  of  the  tubes  or  chambers  has  made  the 
re-entry  of  water  all  the  more  difficult,  so  that  damage  has  nearly 
always  resulted.  (See,  for  example,  Griffiths'  boiler,  p.  374  ante.) 
John  Elder's  Boiler. — This  action  was  evidently  anticipated 
in  such  a  boiler  by  the  late  John  Elder,  whose  patent  of 


FIG.   284. 


THE  MODERN  STEAM  BOILER. 


477 


1862  (No.  1214),  for  a  practically  similar  design  to  that  of 
Matheson,  provides  for  the  introduction  in  the  upper  branch 
from  the  coil  of  a  revolving  screw  to  propel  the  water  down- 
wards through  the  coil.  This  arrangement  is  shown  diagram- 
matically  in  Fig.  285,  which  is  taken  from  Mr.  G.  Halliday's 
"  Steam  Boilers." 

The  patents  of  H.  Chamber- 
lain, 1863  (No.  38),  G.  T. 
Bousfield,  1866  (No.  1913), 
P.  J.  Ravel,  1868  (No.  3479), 

C.  Tyson,    1877    (No.    4811), 
E.T.  Hughes,  1877  (No.  4881), 

D.  Clerk,  1879  (No.  2423),  and 
W.    H.    Northcott,   1880    (No. 
3176),  call  for  no  special  de- 
scription. 

Ward's  Boiler.— C.  Ward's 
patent  of  1879  (No.  4074)  was 
for  the  coil  boiler,  which  he 
commenced  to  introduce  into 
marine  practice  in  America  in 
1877.  This  boiler  is  composed 
of  a  central  vertical  drum  or 
cylindrical  chamber,  which  has 
a  horizontal  branch  at  two- 
thirds  of  its  height,  and  branch 
pipes  connecting  with  two 
horizontal  cylindrical  chests  or 
branches  on  the  floor  line. 
From  these  lower  branches 
vertical  stand  pipes  or  "  water- 
legs  "  rise,  those  under  the  upper 
branch  connecting  directly  with  it,  whilst  those  on  the  other  side 
of  the  central  chamber  have  their  top  ends  closed  by  plugs. 
From  each  side  of  these  stand  pipes  semi-circular  "  coils  "  of 
tubes  proceed,  so  as  to  form  a  number  of  concentric  circles 
around  the  central  chamber.  These  circular  water-tubes  are 
laid  at  a  slight  angle  from  the  horizontal,  so  that  the  flow  of 
steam  will  be  towards  the  stand  pipes,  which  are  connected  with 
the  top  branch  to  the  central  drum.  The  feed  water  is  delivered 


FIG.   285. 


478 


THE  PRACTICAL  PHYSICS  OF 


into  the  central  drum,  in  which  it  descends  to  the  bottom 
branches  and  ascends  by  the  vertical  stand  pipes,  thus  supplying 
the  "  coils."  Figs,  286  and  287  show  this  boiler,  which  was 
fully  described  by  Mr.  Ward  at  the  International  Engineering 


FIG.   286. 

Congress  in  1893.  (Proceedings,  Vol.  ii.  p.  8).  Another  form 
of  Mr.  Ward's  coil  boiler,  which  he  calls  his  "  Launch " 
boiler,  has  the  equivalent  of  the  stand  pipes  in  a  horizontal  posi- 
tion, and  the  coil  tubes  proceeding  in  a  vertical  direction  from 
them. 


THE  MODERN  STEAM  BOILER. 


479 


FIG.  287. 


480 


THE  PRACTICAL  PHYSICS  OF 


Hetreshqff's  Boiler. — Herreshoff's  coil  boiler  was  brought  out  in 
America  in  1877.  It  is  formed  of  an  inner  and  an  outer  coil — the 
outer  one  being  of  comparatively  small  diameter  tube — laid 
together  to  form  the  vertical  cylindrical  sides  and  flat  top  of  the 
boiler  casing.  The  inner  coil  has  a  slightly  conical  outline,  the 
tube  increasing  in  diameter  as  the  coils  descend  towards  the  fire. 
The  layers  of  tube  are  not  placed  close  together,  so  that  the 


BOTTOM  BLOW 


FIG.   288. 

gases  can  escape  between  them.  The  feed  water  is  introduced 
at  the  lowest  point  of  the  outer  coil,  and  traversing  this  is  intro- 
duced into  the  top  of  the  inner  coil,  through  which  it  traverses 
downwards,  the  steam  and  water  being  delivered  into  a  vertical 
separator  cylinder  standing  alongside  the  boiler  casing.  Fig.  288 
illustrates  this  boiler.  A  later  form  of  Herreshoff's  boiler,  which 
is  formed  on  the  type  of  the  Belleville  boiler,  with  flattened 
coil,  composed  of  horizontal  tubes  with  semi-circular  bends, — 


THE  MODERN  STEAM  BOILER.  481 

all  being  exposed  to  heat — is  illustrated  by  Mr.  Ward,  in  his 
paper  on  Tubulous  or  Coil  Boilers  in  Vol.  ii.,  Proceedings  of  the 
International  Engineering  Congress,  plate  xiv.  The  British  patent 
for  the  Herreshoff  boiler  was  taken  out  in  1876  (No.  4271).  It  was 
owned  and  worked  in  this  country  by  Mr.  G.  R.  Dunell,  who 
obtained  a  trial  order  for  it  from  the  British  Admiralty.  Fig.  289 
shows  the  form  of  boiler  finally  adopted  by  Mr.  Dunell  and  the 
Herreshoff  Manufacturing  Co.,  and  interesting  details  connected 
with  the  history  and  performance  of  the  boiler  will  be  found  in 
''  Recent  Practice  in  Marine  Engineering,"  by  W.  H.  Maw,  Vol.  i. 
(Text),  p.  280,  and  in  a  "  Report  of  a  Board  of  U.S.  Naval 
Engineers  on  the  Herreshoff  system  in  the  steam  yacht  Leila" 
made  to  the  Bureau  of  Steam  Engineering  of  the  U.S.  Navy  in 
1881. 

Thoi  nycroff  s  Boiler. — A  coil  boiler  was  patented  by  J.  I. 
Thornycroft  in  1882  (No.  2102),  and  was  referred  to  by  him 
in  his  paper  "  On  Water-tube  Boilers"  in  Min.  Proc.  Inst.  C.E., 
Vol.  xcix,  and  by  Mr.  Wrard,  in  the  paper  above  quoted,  as 
having  been  fitted  in  the  Congo  Mission  steamer  Peace.  Fig.  290 
illustrates  this  boiler,  and  that  this  is  rightly  called  a  coil  boiler 
is  proved  by  Mr.  Thornycroft's  patent,  which  is  for  a  "  coiled 
water-tube  boiler."  In  the  light  of  this  it  is  difficult  to  under- 
stand Mr.  Thornycroft's  remark  on  it  in  Trans.  Inst.  Engineers 
and  Shipbuilders  in  Scotland,  Vol.  xli.,  p.  74. 

There  are  several  other  patents  for  boilers  constructed  of 
coiled  tubes,  but  none  of  these,  excepting  the  De  Laval  boiler 
mentioned  later,  have  come  prominently  forward,  nor  do  they 
illustrate  any  new  features.  The  only  ones  which  merit  a  more 
particular  notice  are  those  of  T.  Craddock,  1884  (No.  5131),  and 
of  O.  Lilienthal  and  W.  Bashall,  1886  (No.  8322)  and  1887  (No- 
T6555).  In  the  former  of  these  two  coils  were  used  and  the  hot 
gases  w^re  led  down  between  the  inner  and  outer  coils  before 
being  allowed  to  escape.  In  the  latter,  the  coil  was  used  to  hold 
the  fuel  as  in  a  gas-producer. 

Cellular  Boilers. — In  the  absence  of  an  extended  manufacture 
of  reliable  tubes,  it  was  natural  that  in  early  days  there  should 
be  several  attempts  to  construct  sectional  boilers  with  a  series  of 
cells  or  small  chambers.  Where,  however,  intricate  smithing  and 
riveting  were  not  resorted  to,  it  is  evident  that  bolts  must  be  used 
to  hold  the  parts  together,  and  this  feature,  with  the  numerous 


482 


THE  PRACTICAL  PHYSICS  OF 


n  o  o  o  o  o  o  o  o 


FIG.   289. 


THE  MODERN  STEAM  BOILER. 


483 


attendant   joints   as   sources    of   leakage,   necessarily    operated 
against  the  success  of  such  boilers. 


feed  D  01,  ve 


FIG.   290. 


Teissier's  Boilers.— The  patent  of  J.  A.  Teissier,  1825  (No.  5251), 
contains  what  may  be  considered  the  first  design  of  such  a 
boiler,  although  James  Rumsey  mentions  a  cellular  form  of 


484 


THE  PRACTICAL  PHYSICS  OF 


boiler  amongst  his  other  plans.  Along  with  the  narrow  chambers 
with  flat  sides  and  roofs  in  Teissier's  boiler,  there  was  the 
notable  feature  of  cylindrical  baskets  or  cages  in  which  the  fuel 
was  placed,  these  being  real  water  grates,  and  having  the 
general  design  of  such  later  boilers  as  those  of  Seabury  and 
others  already  mentioned. 

Hancock's  Boilers. — Walter  Hancock  took  out  at  least  three 
patents  for  cellular  forms  of  boilers  in  1827  (No.  5514),  1833 
(No.  6364),  and  1839  (No.  7990).  These  in  the  main  resulted  in 
his  constructing  the  boiler  illustrated  in  Fig.  291  which  was  used 


MG.    291. 

in  the  steam  omnibuses  of  which  he  was  the  pioneer.  This 
boiler  was  formed  of  a  number  of  narrow  chambers  set  up  on 
edge  side  by  side  and  clamped  together  by  means  of  strong  out- 
side plates  \vith  bearers  and  tie-rods.  Projections  on  the  sides 
of  the  chambers  caused  spaces  to  be  formed  between  each  pair 
of  chambers  through  which,  spaces  the  hot  gases  were  passed. 
Larger  projections  were  also  formed  by  hammering  the  plates 
into  dies,1  which  formed  the  top  and  bottom  transverse  com- 

1  See  "  Reminiscences  of  Steam  Locomotion  on  Common  Roads,"  by  Sir  F. 
Bramwell,  British  Association  Oxford.  1894.  Engineer,  17  Aug.,  1894, 
p.  152,  etc. 


THE  MODERN  STEAM  BOILER.  485 

munication  between  the  chambers.  A  similar  construction  was 
patented  by  Wm.  Church  in  1835  (No.  6791),  but  this  was 
evidently  not  the  boiler  used  by  Church  in  his  coach  (see  ante, 
p.  424). 

Thomas  Brunton  in  1831  (No.  6106),  and  J.  McCurdy  in  1835 
(No.  6819),  both  patented  cellular  forms  which  might  be  used  as 
heaters  connected  with  a  larger  vessel  or  "  boiler:" 

Anderson's  Boiler. — E.  H.  Collier,  1836  (No.  7145),  and  Sir 
J.  C.  Anderson,  1837  (No.  7407),  and  1846  (No.  11273)  ^Iso 
followed  with  designs  of  boilers  composed  of  Hat  leaves  or  cells, 
all  these  being  coupled  as  to  water  and  steam  in  parallel,  although 
the  gases  had  to  pass,  in  some  cases,  over  the  surface  of  the 
cells  in  rotation. 

McCurdy's  Boiler.—].  McCurdy's  patent  of  1838  (No.  7890), 
however,  provided  for  the  coupling  of  the  leaves  in  series  for 
the  How  of  the  water.  He  gives  minute  details  of  the  dimen- 
sions and  performance  of  this  boiler. 

Zander's  Boiler. — H.  Zander  in  1839  (No.  8111)  patented  a 
cellular  boiler  made  of  cast  iron,  in  which  he  has  been  followed 
by  the  Harrison  and  the  Exeter  Boilers,  both  of  which  are 
properly  cellular  boilers.  James  Johnstone,  1843  (No.  9706); 
Chas.  Cowper,  1853  (No.  1247)  ;  and  A.  V.  Newton,  1853  (No. 
2188),  also  add  to  the  list  of  designs  of  this  class,  but  not  of 
those  which  were  used. 

Lamb  and  Summer's  Boilers. — The  boiler  patented  6y  Andrew 
Lamb  and  W.  A.  Summers,  1848  (No.  12362),  1858  (No.  2815), 
and  1859  (No.  2143),  although  of  the  tank  or  box  design,  is 
interesting  from  the  cellular  form  given  to  the  return  flues  or 
passages.  The  construction  of  these  cellular  passages  is  shown 
in  Fig.  292.  This  boiler  was  at  one  time  used  to  some  extent 
in  steamships.1 

Rowan  and  Morton's  Boiler. — In  the  patent  boilers  of  J.  M. 
Rowan  and  T.  R.  Horton,  1858  (No.  856),  1860  (No.  332),  a 
somewhat  similar  form  of  openings  or  passages  was  combined 
with  flat  leaves  or  cells  which  contained  water.  In  addition  to 
these  vertical  openings  there  were  vertical  or  horizontal  tubes 
passing  through  the  water  spaces,  which  tubes  were  used  for 
conducting  the  hot  gases,  or  sometimes  as  water-tubes,  and 

1  See  Proc.  Inst.  Mech.  Eng.     1851.     p.  Q. 


486 


THE  PRACTICAL  PHYSICS  OF 


thus  adding  to  the  area  of  heating  surface.  The  cellular 
openings  were  made  by  bending  and  welding  double-angle 
or  channel  iron,  and  not,  as  in  Lamb  and  Summer's  boilers, 
by  rivetting  a  U-shaped  piece  of  plate  to  the  sides  of  the 
openings. 

This  boiler  is  illustrated  in  Figs.  293,  29313.  It  had  for  about 
12  years  a  very  successful  employment  in  steamers,  of  which  some 
particulars  are  given  in  Chap.  IX.,  but  the  cost  of  construction 
caused  it  to  give  way  to  forms  made  almost  wholly  of  tubes  (see 
p.  431  ante)  as  soon  as  tubes  were  manufactured  of  such  quality 


J'lan  cf  tict 


FIG.    2Q2. 


as  would  enable  them  to  stand  high  pressures  of  steam  in  water- 
tube  boilers.  The  boiler  of  H.  Gourlay  and  E.  Kemp,  1860 
No.  779),  to  some  extent  resembled  the  Rowan  and  Horton 
Boiler,  and  on  this  account  it  was  not  proceeded  with.  The 
patents  of  T.  W.  Miller,  1860  (No.  1396)  ;  G.  Davies,  1860  (No. 
3008)  ;  W.  H.  James,  1862  (No.  3081)  ;  J.  H.  Johnson,  1865 
(No.  2610)  ;  J.  Bernard,  1866  (No.  1410)  ;  C.  L.  Carville,  1867 
(No.  1637)  ;  J.  Witherspoon,  1884  (No.  4657),  for  cellular 
forms  of  boilers,  demand  no  further  notice.  In  fact  the  day  for 
this  class  of  designs  may  be  said  to  have  passed  away,  except  for 
some  special  application,  such  as  the  small  generators  required 
for  motor-vehicles. 


•f  '' 

:  :            i 

j 

m 

i 

li 

1 

I 

! 

I 

i 

FIG.  > ) • V 


423 


THE  MODERN  STEAM  BOILER. 


489 


Panhard  and  Lerassor's  Boilers. — The  cellular  boiler  patented 
by  R.  Panhard  and  E.  Levassor,  1887  (No.  16903),  has  been 
used  for  this  purpose,  as  well  as  others  of  different  design, 
such  as  Serpollet's,  Thornycroft's,  Simpson  and  Bodman's,  and 
De  Laval's. 

Revolving  Boilets. — The  varieties  of  designs  in  which  the 
steam-generating  portion  of  a  boiler  is  caused  to  revolve  in  a 
furnace  date  from  1825,  in  which  year  J.  Thompson  and  J.  Barr 
(No.  5192)  proposed  such  a  design  of  boiler.  They  were  followed 


FIG.    294. 


by  W.  T.  Yates  in  1834  (No.  6547),  G.  Duncan  in  1853  (No. 
502),  D.  Dunn  in  1855  (No.  1223),  G.  Scott  in  1857  (No.  2585),' 
this  being  a  coil  of  tubes  and  not  a  cylindrical  chamber  which 
was  made  to  revolve,  Dr.  F.  Grimaldi  in  1860  (No.  1927)  and 
1861  (Nos.  1641  and  3207),  J.  H.  Johnson  in  1865  (No.  607),  and 
the  Pierce  boiler,  which  was  introduced  in  America  and  was 
amongst  the  boilers  submitted  to  systematic  tests  at  the  Inter- 
national Exhibition  in  Philadelphia  in  1876. 

Pierce  Boiler. — This  boiler  is  illustrated  in  Fig.  294,  and  some 
of  the  results  of  its  tests  will  be  found  in  the  tables  in  Chap.  IX. 

The  most  recent  proposals  in  this  direction  seem  to  be  those 


490  THE  PRACTICAL  PHYSICS  OF 

of  R.  Heber  Radford  in  1892  (No.  153),  and  A.  J.  Boult,  1893 
(No.  12059). 

Porcupine  Boilers. — A  small  class  of  boilers  has  received  the 
name  of  u  porcupine  boilers  "  from  the  peculiarity  of  their  form 
or  appearance.  They  consist  generally  of  a  centra!  chamber 
from  which  cones  or  tubes  project  radially  in  all  directions. 
Sometimes  the  tubes  have  the  straight  form  of  Perkins'  pendant 
tubes  placed  horizontally  with  an  internal  circulation  tube, 
though  in  other  cases  the  internal  tube  is  absent.  In  some 
cases  the  tubes  are  bent  to  form  a  series  of  loops  all  round  the 
central  chamber. 

Gibbs^  Boiler. — The  earliest  of  these  is  that  of  the  patent  of 
Jos.  Gibbs  and  A.  Applegarth  in  1832  (No.  6318)  in  which  cones 
were  used  to  project  into  the  flue  space  in  order  to  increase  the 
heating  surface. 

Joseph  Barrans  in  1852  (No.  41)  also  proposed  to  have  cup- 
shaped  projections  or  deep  corrugations  in  the  plates  of  his  tire 
box,  and  Henry  Bougleux,  1856  (No.  2793),  and  1857  (No.  50), 
repeated  the  same  idea,  making  his  projections,  however,  more 
of  the  shape  of  a  thimble,  and  in  some  cases  piercing  them  by  a 
tube  for  the  products  of  combustion. 

Fletchers  "  Thimble"  Boiler.— H.  A.  Fletcher  in  1869  (No.  998) 
patented  a  boiler  of  this  class  which  was  described  and  illustrated 
in  Engineering,  Vol.  viii.,  p.  38. 

W.  Clark  (for  M.  Hervier),  1882  (No.  4669),  and  E.  S.  T. 
Kennedy,  in  1885  (NOS-  I273>  5768,  13800),  1886  (No.  12282), 
1887  (No.  11673),  and  l888  (Nos-  7°°5>  12780),  repeat  the 
design,  whilst  A.  M.  Clark,  1883  (No.  264)  has  a  modification  of 
it  with  a  number  of  bent  tubes  forming  radial  loops  from  the 
central  chamber. 

The  most  complete  examples  of  the  system  are  E.  S.  T. 
Kennedy's  patent  of  1893  (No.  3486)  ;  the  Minerva  and 
Hazleton  boilers  brought  out  in  America  and  the  "  Climax " 
boiler,  also  an  American  invention,  but  now  manufactured  in 
England. 

Hazleton  Boilers. — There  are  two  forms  of  the  Hazleton  boiler 
manufactured  in  America,  one  called  the  Hazleton  Tripod  boiler, 
made  by  a  Company  of  that  name  in  Chicago,  and  the  other 
called  the  Hazleton  boiler,  made  by  its  Company  in  New  York. 
There  is  not  much  difference  between  the  designs  and  Fig.  295 


THE  MODERN  STEAM  BOILER. 


49 1 


will  suffice  to  illustrate  both.  The  "  porcupine  "  tubes  which 
project  horizontally,  from  the  vertical  stand-pipe  chamber  have 
no  internal  circulating  tubes.  The  difference  between  the  two 
"  Hazleton"  boilers  consists  merely  in  details — the  "Tripod" 
boiler  having  a  branch  man-hole  leg  near  the  bottom  of  the 


FIG.   295. 

central  chamber  and  three  shorter  branches,  like  enlarged 
"  porcupine "  tubes  near  the  top,  with  a  steam  and  water 
separator  in  a  part  of  the  central  chamber  projecting  above  the 
tubes.  The  Hazleton  boiler  illustrated  shows  the  more  simple 
construction. 


492 


THE  PRACTICAL  PHYSICS  OF 


Minerva  Boiler. — In  the  case  of  the  Minerva  boiler  shown  in 
Fig.  296  each  of  the  horizontal  porcupine  tubes  has  an  internal 
circulating  tube  which  projects  from  an  inner  shell  in  the  central 
vertical  chamber,  but  it  seems  apparent  that  in  this  bojler  these 
internal  tubes  are  used  for  conducting  the  steam  into  the  central 
inner  chamber,  whilst  the  water  enters  from  the  outer  division 
of  that  chamber  to  the  larger  porcupine  tubes.  This  cannot  be 


FIG.   296. 

so  good  an  arrangement  as  that  which  uses  the  inner  tube  for 
water,  and  allows  the  steam  to  escape  from  the  mouth  of  the 
outer  tube  in  which  it  is  generated.  The  vertical  chamber  of 
the  Minerva  boiler  is  also  divided  by  horizontal  partitions  to 
form  a  water  chamber,  in  which  the  feed  enters,  above  the 
steam  space.  This  presents  water  to  the  escaping  gases  which 
may  thus  be  cooled  down  below  the  temperature  of  the  steam. 


THE  MODERN  STEAM  BOILER. 


493 


The  steam  pipe  can  also  be  placed  at  a  more  convenient  height 
than  the  top  of  the  boiler.  All  the  water  in  the  top  chamber 
can  be  discharged  into  the  bottom  chamber  almost  instantane- 
ously by  opening  two  valves  on  a  special  pipe. 

Climax  Boiler. — The  Morrin  "Climax"  boiler  has  a  central 
vertical  cylinder  with  radial  loop-shaped  tubes  projecting  from 
its  sides  round  its  complete  diameter,  these  tubes  being  placed 
each  at  a  slight  inclination  so  that  one  end  enters  the  cylinder 
at  a  higher  level  than  the  other  in  order  to  favour  circulation. 
Diaphragm  plates  are  introduced  near  the  top  of  the  cylinder  in 


KIG.   297. 

order  to  cause  the  steam  to  pass  through  several  layers  of  the 
radial  tubes  on  its  way  to  the  steam  dome,  and  thus  to  dry  and 
partially  superheat  it.  Above  the  radial  tubes  a  coil  is  placed  in 
order  to  heat  the  incoming  feed  water.  Figs.  297  and  298 
illustrate  this  boiler  and  fully  demonstrate  its  mode  of  construc- 
tion and  the  manner  in  which  the  looped  tubes  are  arranged. 
This  boiler  was  patented  by  T.  F.  Morrin,  of  New  Jersey,  in  1884 
and  subsequent  years,  and  the  manufacture  of  it  in  Britain 
is  in  the  hands  of  Messrs.  B.  R.  Rowland  and  Co.,  Limited,  of 
Manchester. 

Miscellaneous   Designs. — There    are    some    designs    which   for 
various  reasons  are  more  suitably  considered  apart  from   the 


494 


THE  PRACTICAL  PHYSICS  OF 


classes  which  embrace  a  number  of  boilers  which  have  approxi- 
mately the  same  general  features,  than  as  taking  a  place  amongst 


FIG.  298. 

them.     The  following  examples  seem  to  be  the  most  deserving 
of  notice:  — 


THE  MODERN  STEAM  BOILER. 


495 


In  1836  (Nos.  7059,  7242)  Jacob  Perkins  patented  a  boiler  in 
which  straight  tubes,  hermetically  sealed  at  both  ends,  and  con- 
taining a  small  quantity  of  water  amounting  to  about  T  8Voth  Part 
of  their  capacity,  projected  at  their  lower  ends  into  the  combus- 
tion space  and  at  their  upper  ends  into  the  water  in  a  boiler. 
The  small  quantity  of  water  in  these  tubes  was  rapidly  trans- 
formed into  steam  of  high  pressure,  and  transmitted  heat  into 
the  water  in  which  their  upper  ends  rested.  In  the  later  patent 
he  carried  these  tubes  through  the  boiler  and  used  them  as 
stays  or  tie-bolts.  A  modification  of  this  plan  was  patented  by 
A.  M.  Perkins  in  1855  (No.  2755)  in  which  horizontal  parallel 
coils  were  used,  instead  of 
the  straight  tubes  for  the 
water  heaters.  This  plan 
was  repeated  by  Long- 
bottom  and  Longmaid  in 
1856  (No.  220).  There  was 
not  much  to  recommend  it 
as  a  boiler  design,  but  it  was 
afterwards  utilised  by  Jacob 
and  A.  M.  Perkins  in  the 
construction  of  military  field 
bakers'  ovens,  and  it  has 
been  re-patented  by  Fraser, 
Harris,  and  Perkins  in  1893 
(No.  1206),  and  by  E.  Herz, 
1893  (No.  1467),  and  others. 

Roberts  and  Almy  Boilers. 
— Two    designs,   which    to 

some  extent  resemble  each  other,  are  those  of  the  Roberts  Boiler 
and  the  Almy  Boiler,  both  brought  out  in  America. 

The  Roberts  Boiler  is  shown  by  Figs.  299,  300,  and  301.  It 
is  composed  of  a  frame,  formed  by  downcomer  tubes  from  the 
central  steam  drum  to  the  lowrer  water  pipes  or  drums,  as  shown 
in  Fig.  299.  Within  this  frame  a  number  of  flat  coils  of 
generating  or  "upflow"  tubes  are  placed,  with  a  vertical  position 
starting  from  the  water  pipes  and  forming  the  sides  of  the  furnace. 
These  are  shown  in  position  in  Fig.  300.  In  addition  to  these, 
super-heating  and  feed-heating  coils  are  placed  above  these  coils 
on  each  side  of  the  steam  drum  and  on  the  outside  of  the  boiler 


FIG.   299. 


496 


THE  PRACTICAL  PHYSICS  OF 


;.  300. 


on  the  two  sides  as  shown  in  Fig.  301.     A  casing  envelopes  the 

whole.     This  boiler  was  introduced   in  America   by   Mr.  C.  E. 

Roberts  in  1879,  which  date 
shows  that  Mr.  Roberts  was 
not,  as  he  claimed,1  "  the 
first  inventor  of  boilers  in- 
volving an  upper  steam  and 
water  drum  and  two  lower 
water  drums  at  each  side  of 
the  lire,  connected  by  down- 
How  pipes."  Fig.  302  illus- 
trates the  boiler  made  by  the 
Almy  Water-tube  Boiler  Co., 
of  Providence,  New  York, 
which  bears  a  certain 
amount  of  resemblance  to 
the  Roberts  Boiler. 

Serpollet  Boiler. —  Patents 
were  taken  out  in  Britain  by 

Serpollet   Freres  et  Cie.  in  1880  (No.  1067),   1887  (No.  14710), 

1889   (No.  5197),  1890   (No.   12164),  iind    l894  (No-  997).  for 

different  forms  of  flash  boilers, 

the  last  being  the  form  adopted 

in  France  for  use  in  their  steam 

automobiles.       This    boiler    is 

formed  of   tubes   having  con- 
siderable   thickness    of    metal, 

with  a  very  small,  or  "  capillary  " 

passage  for  the  water  or  steam. 

In  one  form  these  tubes  were 

flat   in    section    and  bent   into 

a    coil     shape     as    shown    in 

Fig-  303- 

A  later  form,  however,    has 
the   tubes    straight,    but    of    a  KM-..  301. 

horseshoe   section,   giving   the 

capillary  space    a    crescent  form,  except   at   their  ends,  which 
are   left   round   in    order  to  make  connection  with  the  bends. 


Proc.  Internal.  Engineering  Congress,  Chicago,  1893,  Vol.  ii.,  p.  74. 


THE  MODERN  STEAM  BOILER. 


497 


This  design  is  shown  in  Fig.  304.  Through  the  small  passages 
or  slits  in  the  pipes  water  is  forced  and,  the  quantity  being 
so  small  in  relation  to  the  mass  of  metal  which  retains  a 
considerable  amount  of  heat,  the  water  is  almost  instan- 
taneously Hashed  into  steam,  which  is  superheated  by  further 
passage  through  the  heated  tubes.  By  varying  the  rate  at 


VIG.   302. 


which  water  is  forced  in,  the  quantity  of  steam  produced  can 
be  altered  at  will.  The  tubes  are  made  of  steel  and  are  tested 
to  200  atmospheres,  the  working  pressure  of  the  boiler  being 
about  350  Ibs.  per  sq.  inch.  It  is  sometimes  urged  against  this 
system  that  the  high  temperature  to  which  the  tubes  are  exposed 
causes  comparatively  rapid  oxidation  and  that  cleaning  the 
narrow  passages  by  means  of  the  use  of  an  acid  solution  has  to 

KK 


498 


THE  PRACTICAL  PHYSICS  OF 


be   resorted  to,  but  it  does  not  appear  on  what  records   this 
objection  is  founded. 


FIG.   303. 

Thornycroft  Boiler. — A  modified  form  of  Thornycroft  Boiler, 
which  has  been  used  by  the  inventor  for  steam  automobiles,  was 
patented  in  1894  (No.  18,838).  A  some- 
what similar  design  is  illustrated  in  Ber- 
tin  and  Robertson's  "  Marine  Boilers '' 
(page  314)  and  is  ascribed  to  Leblond 
and  Caville  (1896),  and  it  is  not  unlike 
the  stationary  boiler  of  Rowan  and 
Horton's  patent  of  1869.  Leblond  and 
Caville's  British  patent  is  dated  1895 
(No.  9444). 

De  Lavals1  Boiler. — Some  particulars 
of  an  interesting  boiler  invented  by 
Dr.  de  Lavals,  of  Stockholm,  have 
appeared  in  the  Electrical  Engineer  of  FIG.  304- 


THE  MODERN  STEAM  BOILED  499 

New  York  (November  nth,  1897),  and  in  Engineering  of 
November  26th,  1897  (pp.  644-645).  This  boiler  is  intended 
for  use  in  conjunction  with  the  De  Lavals  steam  turbine,  the 
peculiar  design  of  which  enables  steam  of  very  high  pressure 
to  be  used  without  causing  any  attendant  difficulties  as  to  tight 
joints  or  lubrication  to  be  experienced  in  the  engine.  The 
different  types  of  these  boilers  which  have  been  constructed 
work  at  pressures  of  from  50  to  220  atmospheres,  one  shown 
in  action  at  the  Stockholm  Exhibition  in  1897  worked  at 
1,700  Ibs.  per  square  inch  pressure,  the  temperature  of  the 
steam  being  about  600  F.  The  steam-space  and  water-space  in 
the  boiler  are  very  small,  and  as  a  consequence  the  boiler  is 
extremely  sensitive  to  variations  in  the  load,  so  that  the 
arrangements  for  working  it  present  the  nearest  approach  to 
complete  automatic  regulation  which  has  been  made.  The 
boiler  consists  of  a  single  tube,  of  solid-drawn  malleable  iron 
of  comparatively  small  diameter,  wound  in  concentric  spirals 
between  which  the  gases  of  combustion  escape.  The  tubes  are 
submitted  to  a  hydraulic  pressure  of  more  than  double  the 
working  steam  pressure  before  being  used.  The  grate  is  shaped 
like  a  ring  and  has  a  revolving  motion,  and  the  coals  are  filled  in 
centrally  from  boxes  above  the  boilers.  These  boxes  need  not 
be  rilled  more  than  once  in  every  two  or  three  hours,  but  the 
layer  of  fuel  in  the  furnace  is  kept  automatically  at  a  constant 
thickness.  The  air  necessary  for  combustion  is  forced  into  the 
furnace  by  means  of  a  fan  which  is  coupled  direct  to  the  driving 
shaft  of  the  turbine,  and,  by  means  of  an  apparatus  regulated  by 
the  steam  pressure  and  acting  on  the  valves  of  the  blast,  the 
combustion  is  regulated  according  to  the  quantity  of  steam 
consumed.  The  feed  water  is  pumped  continuously  into  one 
end  of  the  tube  and  passes  through  the  spirals  one  after  the 
other  with  considerable  velocity,  forming  steam  which  is  super- 
heated in  the  final  portions  of  the  spirals  from  which  it  passes 
to  the  turbine,  there  being  no  steam  chamber  or  reservoir. 
Special  regulating  apparatus  is  also  employed  to  cause  the  feed 
pump  to  feed  into  the  boiler  as  much  water  as  the  turbine  uses 
as  steam,  so  that  the  proportions  of  water  and  steam  in  the 
boiler  and  the  degree  of  super-heat  are  kept  constant.  The 
exceedingly  powerful  circulation  of  water  in  the  boiler  renders 
the  heating  surface  very  effective,  and  this,  coupled  with  the  fact 


500 


THE  PRACTICAL  PHYSICS  OF 


of  the  small  steam  and  water  spaces  referred  to,  has  made  it 
possible  to  bring  the  dimensions  of  the  boiler  within  a  small 
compass.  It  is  stated  that  a  combined  100  horse  power  turbo- 
generator with  suitable  boiler  and  condenser  occupies  a  floor 
space  of  only  18  ft.  6  in.  by  n  ft.  The  boiler  is  self-contained, 
requiring  no  brickwork  except  the  foundation.  The  air  supply- 
passes  through  an  outer  shell,  whereby  it  absorbs  the  radiant 


FIG.   305. 


heat,  or  at  any  rate  prevents  loss  by  radiation,  and  the  use  of  the 
air-blast  also  has  tended  to  reduce  considerably  the  size  of 
chimney  required.  No  illustration  of  this  boiler  has  been  as  yet 
made  public,  except  that  in  Dr.  de  Lavals'  British  patent, 
Specification  No.  14884-1895  (see  Fig.  305),  but  the  description 
shows  that  it  embodies  a  very  great  advance  towards  a  perfect 
steam-generating  apparatus. 


THE  MODERN  STEAM  BOILER.  501 

Simpson  and  Bodman  Boiler. — Early  in  1898,  Messrs.  D.  H. 
Simpson  and  W.  L.  Bodman  communicated  to  the  Liverpool 
Centre  of  the  Self -Propelled  Traffic  Association  an  account 
of  various  interesting  trials  and  experiments  carried  out  by 
them  to  determine  the  best  types  of  boilers  and  motors  for 
steam  road  vehicles.  Probably  the  most  interesting  attempt 
to  construct  an  efficient  flash  boiler  is  the  one  which  is 
illustrated  by  Fig.  306,  in  which  the  Row  patent  indented 
tubes  were  employed,  their  wavy  form,  resulting  from  the 
tubes  being  pressed  between  dies  alternately  at  right  angles, 
causing  the  water  to  come  into  intimate  contact  \vith  the 
heating  surface.  The  tubes  used  were  of  solid-drawn  steel,  with 
the  ends  swaged  down  so  as  to  form  practically  stout  double- 
ended  gas  bottles.  Twenty-two  such  tubes  were  used  in  the 
construction  of  a  boiler  to  evaporate  about  300  Ibs.  of  water 
per  hour.  They  were  coupled  in  series  over  the  fire,  being 
connected  by  steel  tube  bends.  The  ends  of  the  main  tubes 
were  screwed  with  eleven  threads  to  the  inch,  and  the  bends 
fourteen  to  the  inch.  A  strong  hexagon  nut,  screwed  to  fit 
the  bend  at  one  end  i  and  the  tube  at  the  other,  being  used  to 
draw  the  bend  up  the  tube,  the  difference  in  threads  gave  a 
pull  equivalent  to  an  ordinary  union  nut  with  51  threads  per 
inch,  and  the  strength  of  14.  Forty-four  joints  made  in 
this  way  stood  800  Ibs.  hydraulic  test  at  the  lirst  time  of 
screwing  up. 

The  tubes  are  placed  horizontally  over  the  ,fire  in  a  suitable 
casing.  Connected  to  the  steam  outlet  end  is  a  double-ended 
steel  gas  bottle,  which  has  a  tube  passing  through  its  centre, 
through  which  the  feed  water  passes  in  its  way  to  the 
generator.  It  is  thus  heated,  removing  some  of  the  super- 
heat of  the  steam,  and  increasing  the  duty  of  the  boiler  by 
the  introduction  of  hot  feed.  After  the  boiler  has  been  standing, 
or  when  the  steam  is  very  hot,  water  is  sprayed  into  the 
drum,  when  it  is  evaporated  by  the  extra  heat  in  the  super- 
heated steam,  and  pusses  on  to  the  engines.  This  system 
of  injecting  water  into  the  steam  and  cooling  it  down  to  a 
reasonable  temperature,  while  still  leaving  the  boiler  hot  as  a 
reserve  of  heat,  has,  according  to  Messrs.  Simpson  and  Bodman, 
overcome  one  of  the  greatest  difficulties  in  this  type  of 
boiler.  The  system  of  starting  and  working  is  explained  by 


502 


THE  PRACTICAL  PHYSICS  OF 


FIG.  306. 


THE  MODERN  STEAM  BOILER. 


503 


FIG.   307. 


THE  PRACTICAL  PHYSICS  OF 


THE  MODERN  STEAM  BOILER.  505 

the  diagram  Fig.  307  with  the  following  notes  : — The  generator  is 
raised  to  a  black  heat,  say  800°  F.  A  stroke  or  two  of  the 
hand  pump  H.S.P.  sends  the  water  up  the  pipe  P.D.  The 
injector  valve  I.S.V.  is  opened,  and  a  small  amount  of  water 
allowed  to  enter  the  drum  I.D.  The  valve  I.S.V.  is  then  closed, 
and  the  water  travels  through  the  feed  heating  tube  F.H.T. 
in  the  centre  of  drum  I.D.,  and  on  through  the  feed  pipe 
F.P.  into  the  generator.  The  superheated  steam  then  passes 
into  the  drum  I.D.,  where  any  excessive  superheat  is  extracted 
by  the  feed  water  passing  through  the  central  tube,  and  by  the 
water  injected  into  the  drum.  The  hand  pump  is  worked 
until  the  water  relief  valve  S.R.V.,  which  is  set  to  working 
pressure,  starts  returning  the  surplus  water  to  the  feed  \vater 
tank  F.W.T.  Then  the  main  stop  valve  M.S.V.  may  be 
opened,  starting  the  engines,  which  work  their  own  pumps 
E.P.,  keeping  up  the  supply  of  water,  any  surplus  being 
returned  by  the  relief  valve. 

Controlling  the  feed  by  a  steam  pump,  used  in  conjunction  with 
a  live  steam  feed  heater,  the  water  from  the  purnp  exhaust  being 
drained  back  to  the  feed  tank,  was  preferred  to  any  automatic 
gear.  Fig.  308  shows  the  most  recent  form  of  this  boiler  from 
the  working  drawings.  The  illustration  shows  a  boiler  composed 
of  12  "members"  of  weldless  steel  tubes — these  "members" 
being  U-shaped,  the  straight  portions  being  indented  on 
the  Row  plan,  and  the  bends  being  smooth  and  smaller  in 
diameter.  The  only  joints  are  thus  made  at  the  front  of  the 
boiler,  or  at  one  side,  the  system  of  making  the  joints  being  that 
introduced  in  the  Hay  thorn  boiler.  The  water  is  fed  direct 
from  the  pump  into  the  top  row  of  tubes  in  the  generator, 
and  issues  from  the  second  row,  having  traversed  the  four 
uppermost  U-tubes.  It  then  passes  through  a  U-shaped  tube 
inserted  in  the  steam  regulating  drum,  and  thence  passes  to  the 
bottom  row  of  tubes  and  passes  out  from  the  fourth  row 
from  the  bottom  as  superheated  steam,  which  is  collected  in 
the  steam  drum. 

The  patents  for  the  Simpson  and  Bodman  boiler  are  dated 
1896  (Nos.  4485  and  4486). 

Some  particulars  of  tests  of  this  flash  boiler  are  given  in 
Chap.  IX.,  but  by  forcing,  the  evaporation  can  readily  be 
increased  to  500  Ibs.  of  water  per  hour. 


506  THE  PRACTICAL  PHYSICS  OF 

Boilers  with  Gas  Producers. — Several  designs  have  been 
proposed  in  which  the  mass  of  fuel,  instead  of  being  wholly 
spread  on  a  grate,  is  held  by  portions  of  the  boiler,  which 
thus  enclose  it  somewhat  in  the  manner  of  the  walls  of  a 
gas  producer.  The  labour  of  stoking  is  thus  rendered  easier, 
and  the  fuel  before  reaching  the  zone  of  combustion  is 
partially  heated,  and  may  even  be  partially  distilled,  the 
gases  thus  given  off  being  subsequently  ignited  when  means 
for  the  admission  of  air  are  present  along  with  sufficient 
combustion  space.  The  attempt  to  combine  the  functions 
of  a  gas  producer  with  those  of  a  boiler  is  not,  however,  a 
very  promising  one,  if  for  no  other  reason,  because  an  efficient 
gas  producer  demands  combustion  at  a  comparatively  low 
temperature,  whilst  the  utilisation  of  the  fuel  in  a  boiler 
requires  that,  as  we  have  seen,  combustion  shall  take  place 
at  the  highest  possible  temperature,  and  it  will  be  extremely 
difficult  to  reconcile  such  opposing  conditions  in  one  apparatus. 

Part  of  the  idea  is  contained  in  Paul's  patent  of  1824  (see 
p.  361  ante),  whilst  William  Church  in  1832  (No.  6220)  proposed 
a  boiler  composed  of  vertical  tubes,  set  in  circular  rows  round  a 
grate,  the  fuel  being  filled  in  from  the  top  ;  and  C.  Johnson 
in  1868  (No.  2021)  proposed  another  form  for  a  similar 
arrangement.  In  1884,  B.  C.  Sykes  and  T.  Briggs  (No.  2709), 
and  J.  W.  Macfarlane  and  J.  J.  Coleman  (No.  12497)  combine 
boilers  with  enclosed  gas  producers  fed  from  above. 

In  1886,  O.  Lilienthal  and  W.  Bashall  (No.  8322)  have  a  coiled 
water-tube  boiler  with  the  fuel  arranged  as  in  a  gas  producer 
enclosed  in  the  coil.  Their  subsequent  patent  in  1887  (No. 
16555)  was  abandoned.  J.  J.  Barclay  in  1889  (No.  11864)  com- 
bined a  shell  boiler  with  a  similar  arrangement  for  the  fuel 1  and 
G.  H.  Taylor,  1889  (No.  14708)  had  a  gas  producer  combined 
with  a  vertically  inclined  water-tube  boiler.  About  1886 
B.  H.  Thwaite  proposed  the  combination  of  a  boiler  with  his 
gas  producer,  but  in  this  case 2  the  boiler  was  placed  above  the 
gas  producer  and  formed  the  combustion  chamber  for  the  gas 
which  was  produced  below. 

1  Another  will  be  found  illustrated  in  The  Mechanical  Engineer  of  Qth 
April,  1898,  page  368. 

2  See  Min.  Proc.  Inst.  C.E.,  Vol.  Ixxxiv.,  p.  105. 


THE  MODERN  STEAM  BOILER.  507 

Other  designs  which  have  been  proposed  are  those  of  W. 
Schmidt,  1893  (No.  564)  ;  L.  Bemelmans,  1893  (No.  1290)  ;  E. 
Herz,  1893  (No.  1467)  ;  G.  H.  Taylor,  1893  (No.  7510)  ;  C.  A. 
Allison,  1893  (No.  9077)  ;  L.  Benier,  1893  (No.  64),  1894  (No. 
6744)  ;  J.  M.  White  and  J.  Timmins,  1894  (No.  7934)  ;  S.  S. 
Bromhead,  1896  (No.  4674)  ;  De  Laval,  1895  (No.  14884)  ; 
Newton,  1895  (No.  22023),  &c. 

The  latest  proposal  is  that  of  Professor  W.  H.  Watkinson  in 
1898  (No.  13328)  who  uses  the  vertical  tubes  of  his  boiler,  which 
is  described  in  his  specification  of  1896  (No.  15721),  to  form  two 
sides  of  a  gas  producer.  The  other  two  sides  may  be  built  of 
brick  or  of  walls  of  tubes.  The  fuel  is  fed  in  at  the  top  through 
a  hopper  placed  between  the  two  horizontal  drums  from  which 
the  tubes  descend.  A  special  trough-shaped  casting  with  grids 
along  the  sides  forms  the  grate.  In  outline  the  boiler  is  similar 
to  that  of  the  land  boiler  shown  in  Rowan  and  Horton's  specifi- 
cation of  1869,  two  of  these  latter  elements  (used  also  by  the 
author  in  1894,  No.  8170)  being  placed  side  by  side,  but 
Professor  Watkinson  arranges  his  vertical  tubes  very  closely 
side  by  side  in  order  to  allow  only  very  thin  sheets  or  streams  of 
hot  gases  to  pass  through.  The  object  of  this  arrangement  is  to 
imitate  the  well-known  cooling  action  of  wire-gauze  on  flame, 
but  unless  some  means  were  provided  for  re-igniting  the  cooled 
gases  on  the  far  side  of  such  a  wall  of  tubes  it  is  probable  that 
much  of  the  combustible  gas  might  escape  unconsumed.  It  is 
well-known  that  whilst  a  flame  cannot  pass  through  wire  gauze, 
it  is  still  possible  to  ignite  the  gases  on  the  opposite  side  of  the 
gauze,  and  this  result  will  even  be  automatically  accomplished 
as  soon  as  the  wire  gauze  becomes  red  hot.  If  complete  com- 
bustion took  place  before  the  gases  were  passed  through,  the 
first  row  of  tubes  there  would  completely  screen  the  heat  from 
the  rest  of  the  boiler  surfaces. 

Several  designs  of  boilers  due  to  French  inventors  will  be 
found  alluded  to  in  Bertin  and  Robertson's  "  Marine  Boilers  "  at 
page  282,  and  in  "  Les  Chaudieres  Marines "  by  M.  L.  De 
Chasseloup-Laubat  in  the  Memoires  de  la  Societe  des  Ingenieurs 
Civils  de  France,  for  April,  1897. 

General  Observations. — There  can  be  little  doubt  that  in  propor- 
tion as  we  apprehend  the  importance  of  the  principles  which 
are  dealt  with  in  the  preceding  chapters,  we  shall  be  able  to 


5o8  THE  PRACTICAL  PHYSICS  OF 

estimate  the  value  of  the  different  designs  that  are  proposed, 
according  as  they  exhibit  the  varying  degrees  in  which  true 
principles  are  applied,  and  to  discriminate  between  different 
designs.  In  many  of  the  cases  which  have  been  before  us  we 
have  no  record  of  the  pressure  of  steam  at  which  it  was  intended 
to  work  the  boiler,  so  that  only  the  forms  can  be  compared 
generally  in  view  of  the  action  of  steam  raising,  and  partially  in 
relation  to  strength.  It  must  not  be  forgotten  that  whilst  the 
boiling  of  water  in  an  open  vessel,  or  at  atmospheric  pressure,  is 
an  action  which  proceeds  strictly  on  natural  lines,  when  we 
employ  a  closed  vessel  and  higher  pressures  of  steam  we  have 
introduced  conditions  which  render  steam-raising  more  or  less 
an  artificial  process,  which  must  be  conducted  in  accordance 
with  scientific  principles,  the  carrying  out  of  which  process 
demands  frequently  the  highest  engineering  skill  for  its  success- 
ful manipulation  and  control.  On  this  account  it  is  apparent 
that  one  without  training  or  experience  can  no  more  handle  or 
judge  of  a  scientific  steam  generating  apparatus,  than  can  an 
ordinary  mill-wright  manipulate  the  finer  mechanism  of  a  watch 
or  a  delicate  electrical  machine.  Actions  that  are  incongruous 
with  steam  generation  should  be  rigidly  excluded  from  the 
steam  generator,  and,  to  take  one  marked  instance,  it  is  incon- 
trovertible that  the  separation  of  solid  matters  of  any  description 
from  the  water  is  not  an  operation  which  should  be  carried  on 
in  an  apparatus  designed  for  steam  generation.  All  treatment 
of  the  water  from  which  steam  is  to  be  produced,  whether  for 
purification  or  for  the  prevention  of  incrustation  or  corrosion, 
should  be  carried  out  in  vessels  external  to  the  boiler.1  It  is 
absurd  to  expect  that  an  efficient  steam  generator  should  also 
act  as  a  precipitating,  filtering  or  mud-collecting  apparatus.  The 
conditions  which  are  essential  to  the  highest  efficiency  in 
generating  steam  are  sufficiently  complex  and  onerous  to  demand 
that  the  boiler  shall  be  entirely  devoted  to  them. 

After  the  problem  of  combustion  is  mastered,  there  are  two 
great  factors  which  govern  all  considerations  leading  to  the 
determination  of  the  best  design,  viz.  : 


1  On  this  subject  see  the  excellent  Report  on  the  Purification  of  the  Feed 
Water  of  Locomotives  presented  by  Mr.  J.  A.  F.  Aspinall  to  the  Sixth  Session 
of  the  International  Railway  Congress  held  in  Paris  during  1900. 


THE  MODERN  STEAM  BOILER.  509 

ist,  the  movement  of  the  hot  gases,  or  the  application  of  the 
heat  presented  for  transmission  in  the  best  way,  and 

2nd,  the  movement  of  the  water,  or  circulation  of  the  heat 
recipient,  so  that  heat  may  be  most  freely  received  and  steam 
most  readily  liberated  and  the  boiler  surfaces  preserved. 

There  are  sub-factors,  such  as  strength  (involving,  of  course, 
safety),  lightness,  durability  and  economy,  which  include  the 
question  of  the  necessity  for,  and  facility  of  executing  repairs, 
but  there  is  no  reason  why  these  should  not  be  easily  pro- 
vided for  if  they  are  kept  subordinate  to  the  others.  It  has 
been  too  much  the  practice  to  place  those  first  which  should 
be  subordinate,,  and  those  last  which  should  be  first.  In 
the  past,  with  chimney  draught,  facility  of  combustion  was  no 
doubt  naturally  the  first  consideration,  and  the  most  convenient 
aiTfingement  probably  was  one  that  permitted  the  gases  to  con- 
tinually ascend.  Hence  horizontal  or  horizontally  inclined 'tubes 
seemed  to  present  their  surfaces  in  the  best  position  to -the 
stream  of  hot  gases.  Even  then,  however,  good  results  were 
obtained  with  vertical  tubes  or  surfaces  by  directing  the  course 
of  the  gases  to  and  fro  horizontally  and  even  downwards.  With 
mechanically  moved  gases  we  can  command  their  direction  of 
movement,  and  have  the  opportunity  of  considering  primarily 
the  means  of  utilising  to  the  best  advantage,  and  even  of  aiding, 
the  movement  of  the  water  and  steam. 

Different  theories  of  the  course  followed  by  the  steam  and 
water  under  the  action  of  the  heat  of  the  fuel  have  been  the 
cause  of  several  vagaries  of  design,  but  the  introduction  of 
mechanical  movement  of  the  water  will  here  also  leave  nothing 
to  chance,  and  will  ensure  the  realisation  of  the  best  conditions 
for  working  and  for  preservation  of  the  boiler.  It  is  not  un- 
likely that,  for  the  higher  temperatures  which  must  probably  be 
faced  in  connection  with  steam  generation,  some  adaptation  of 
a  film  system,  differing  from  that  of  Serpollet  and  that  of 
Simpson  and  Bodman,  will  be  combined  with  such  forced 
circulation  of  the  water.  And  if  properly  arranged,  the  division 
of  the  streams  of  hot  gases  also  into  thin  films  will  no  doubt 
be  found  advisable. 

A  survey  of  the  many  designs  published  in  the  past  leads  to 
the  conclusion  that  there  are  in  the  main  five  distinct  arrange- 
ments in  water-tube  designs  which  are  practically  possible,  viz., 


510  THE  PRACTICAL  PHYSICS  OF 

first,  vertical  tubes ;  second,  inclined  tubes  ;  third,  coils  ;  fourth, 
horizontal  tubes,  parallel  coupling ;  and  fifth,  horizontal  tubes, 
series  coupling.  There  may  be  modifications  of  these,  or  com- 
binations of  one  with  another,  but  all  boilers  may  be  classed 
under  these  heads  if  the  main  features  of  design  are  taken  into 
account,  and  we  believe  that  we  have  here  placed  them  in  the 
distinct  order  of  their  value. 


CHAPTER  IX. 

SOME  TESTS  OF  BOILERS  AND  RESULTS. 

IT  is  obviously  impossible  within  the  limits  of  such  a  work  as 
this  to  give  a  record  of  trials  of  all  the  boilers  referred  to  in 
it.  On  this  account  a  comparatively  small  number  of  such  trials 
must  be  selected  because  of  their  possessing  some  features  of 
special  interest,  either  technical  or  historical.  Some  elements 
of  comparison  of  different  designs  can  be  derived  from  such 
records,  but  a  large  number  of  details  must  be  known  before 
a  complete  or  trustworthy  comparison  can  be  instituted  between 
boilers  differing  widely  in  design. 

The  published  proceedings  of  the  Industrial  Society  of  Mul- 
house,  and  of  the  Royal  Agricultural  Society  of  England,  contain 
valuable  information  regarding  the  testing  of  steam  boilers  of 
different  types  ;  and  recent  practice  is  shown  in  Donkin  and 
Kennedy's  "  Tests  of  Steam  Boilers  "  ;  "  The  Heat  Efficiency  of 
Steam  Boilers,"  by  Bryan  Donkin  ;  Professor  Thurston's"  Manual 
of  Steam  Boilers "  (chap,  xiv.),  and  in  "  The  Marine  Steam 
Engine,"  by  Sennett  and  Oram  (p.  85,  etc.).  Wm.  Kent's 
"  Steam  Boiler  Efficiency  "  should  be  studied  in  this  connection, 
and  reference  should  be  made  to  the  new  standard  tests  of 
which  some  notice  will  be  found  in  Min.  Proc.  Inst.  C.  E., 
Vols.  cxli.,  p.  383,  and  cxlii.,  pp.  414-419. 

Of  late  years  controversy  has  raged  between  the  advocates  of 
the  cylindrical  or  Scotch  form  of  boiler  and  those  who  support 
the  introduction  and  use  of  water-tube  designs.  Personal  or 
vested  interests  have  as  usual  imported  some  bitterness  into  such 
controversy  and  prevented  the  question  being  debated  solely  on 
its  scientific  merits,  with  consequent  loss  to  all  concerned.  And 
it  has  frequently  been  forgotten  that  in  very  few  cases  are  the 
records  of  tests  or  catalogues  of  results  sufficiently  full  and 
ample  to  justify  any  final  conclusion  as  to  the  comparative 
merits  of  the  different  designs.  Moreover,  it  should  be  re- 
membered that  whilst  it  is  unlikely  that  any  great  improvement 
in  construction  or  working  can  now  be  introduced  in  the  case  of 

5" 


512  THE  PRACTICAL  PHYSICS  OF 

the  cylindrical  boiler,  in  that  of  the  water-tube  boiler  there  is 
not  only  room  for  improvement  but  great  likelihood  that  im- 
proved forms  will  be  introduced  as  experience  with  this  type 
becomes  extended.  It  is  sometimes  urged  that  the  possibilities 
of  forced  combustion  with  the  cylindrical  boiler  have  not  yet 
been  fully  investigated  ;  but,  as  we  have  seen  in  Chapter  IV., 
etc.,  improvement  in  methods  of  combustion  can  apply  with 
greater  force  and  readiness  to  the  water-tube  than  to  the  other 
design.  It  may  be  admitted  that  few,  if  any,  of  the  water-tube 
boilers  hitherto  actually  introduced  could  profit  by  a  develop- 
ment of  forced  combustion,  but,  on  the  other  hand,  should  im- 
provement in  methods  of  combustion  be  introduced,  the  water- 
tube  system  undoubtedly  presents  more  flexibility  of  adaptation 
to  new  conditions  than  does  its  rival. 

Regarding  the  utilisation  of  the  heat  of  the  fire  gases,  the 
degree  to  which  that  is  possible  with  the  different  systems  turns 
largely  upon  the  question  whether  conducting  these  gases 
through  tubes  which  are  surrounded  with  water,  or  dispersing 
them  amongst  tubes  which  are  filled  with  water,  is  the  more 
efficient  arrangement.  There  are,  of  course,  good  points  in  both, 
but  the  considerations  advanced  in  the  preceding  chapters  un- 
doubtedly show  that  the  latter  offers  the  best  prospect  of  a 
satisfactory  result  from  the  point  of  view  of  heat  transmission 
efficiency.  It  is  but  fair  to  add  that  such  a  result  as  is  here 
contemplated  has  not  yet  been  realised  from  any  boiler  of  what- 
ever design  hitherto  introduced,  although  some  water-tube  boiler 
trials  have  shown  a  higher  rate  of  evaporation  per  square 
foot  of  heating  surface  than  has  been  obtained  with  cylindrical 
boilers. 

Payne's  Result. — A  reference  to  what  is,  perhaps,  the  oldest 
evaporative  result  on  record  shows  how  very  small  an  advance 
has  been  made  in  utilisation  of  heat  during  150  years.  John 
Payne,  in  describing  his  steam  boiler  to  the  Royal  Society  of 
England  in  1747  (see  Phil.  Trans.,  1747,  page  828),  announced 
that  he  had  "  rarefied  "  or  turned  into  steam  90  gallons  of  water 
with  112  Ibs.  of  coal.  This  having  been  an  evaporative  rate  of 
8'O3  Ibs.  of  water  per  Ib.  of  coal,  is  not  very  far  behind  the 
best  results  obtained  to-day. 

Mulhouse  Trials. — Amongst  the  results  given  in  the  "  Bulletin 
de  la  Societe  Industrielle  de  Mulhouse  "  (Vol.  xliii.,  1873)  tnere 


THE  MODERN  STEAM  BOILER. 


513 


are  the  following  comparative  results  obtained  in  1872  in  trials 
with  Cornish,  Lancashire,  and  French,  or  "  Elephant  "  forms  of 
boilers  : — 


TABLE  LXVI. 


Cornish. 

Lancashire 

French. 

Coal  per  hour 

Ibs. 

216 

244 

387 

„       sq.  ft 

.  of  grate       ,, 

15 

I3-2 

14-4 

Water  per  Ib. 

of  coal           ...         ...         ...      ,, 

7-66 

7'80 

7-28 

M 

combustible         ...         ...      „ 

8-89 

8-99 

8-20 

Later  comparative  trials  of  Lancashire,  Fairbairn,  and  French 
forms  of  boilers,  published  by  the  same  society/  also  yield  inte- 
resting results,  as  do  the  experiments  carried  out  by  Mr.  Isher- 
wood 2  on  a  marine  boiler  w7ith  proportions  of  fire-grate  and 
heating  surface  varied  at  will. 

IsherwoocVs  Trials. — From  our  point  of  view  in  this  volume, 
however,  more  practical  information  is  yielded  by  the  trials  of  a 
horizontal  flue  tube  and  a  vertical  water-tube  boiler  (the  latter 
being,  however,  only  a  tank  boiler  with  vertical  wrater-tubes 
inserted  in  a  large  flue)  on  board  the  U.S.  steamer  "  San  Jacinto." 
The  grate  area  (108  sq.  ft.)  was  the  same  in  both  boilers,  and 
the  ratio  of  grate  area  to  heating  surface  was  i  to  24!  in  the 
flue  boiler  and  i  to  30  J  in  the  water-tube  boiler. 

The  water- tube  arrangement  showed  more  rapid  evaporation 
and  more  efficient  heat  utilisation  than  the  other  form.  The 
following  are  the  results  with  normal  condition  of  heating 
surface  in  both  boilers.  They  show  that  the  water-tube 
arrangement  evaporated  10*3  per  cent,  more  water  per  hour 
and  1 8*8  per  cent,  more  per  pound  of  coal,  and  showed  a  tem- 
perature of  waste  gases  fully  -100°  lower,  than  in  the  flue-tube 
arrangement. 

1  See  also  "  The  Steam  Engine,"  by  D.  K.  Clark,  Vol.  i.,  pp.  213-231. 

2  Experimental    Researches  in    Steam    Engineering.     New    York.     1865. 
Vol.  ii. 

S 


THE  PRACTICAL  PHYSICS  OF 
TABLE  LXVII. 


Natural  Draught. 

Forced  Draught. 

Flue  tube. 

Water  tube 

Flue  tube. 

Water  tube 

Coal  per  sq.  ft.  of  grate  per  hour 

12-6  Ibs. 

117  Ibs. 

24-5  Ibs. 

23-7  Ibs. 

Ash  per  cent 

. 

I43 

16-8 

I4-8 

16-3 

Water  at  212 

0  evaporated  per  hour 

i2055lbs. 

I330ilbs. 

i7425lbs. 

18564^5. 

))                      M 

„           ,,  .     Ib.  of  coal 

8-87  Ibs. 

10-54  Ibs. 

6-57  Ibs. 

7-26  Ibs. 

»                      » 

„            ,,    combustible 

1  0-35  Ibs. 

12-67  Ibs. 

6-92  Ibs. 

8-68  Ibs. 

Temperature 

in  uptake    ... 

462°  F. 

356°  F. 

... 

Air  pressure 

at  blower 

I  -54  ins. 

1-54  ins. 

Similar  results,  but  on  a  more  elaborate  scale,  are  shown  in 
the  following  tables  recording  further  trials  of  t\vo  marine 
donkey  boilers  in  the  U.S.  Navy  Yard,  New  York  ;  one  of  these 
boilers  having  an  ordinary  horizontal  tire-tube,  and  the  other 
having  vertical  water-tubes  on  Martin's  plan,  as  in  the  "  San 
Jacinto's  "  boilers. 

Although  Martin's  boiler  was  not  a  true  water-tube  boiler,  but 
was  only  a  tank  boiler  fitted  with  vertical  water-tubes  in  the 
large  horizontal  return  flue,  yet  in  these  trials  it  showed  a 
higher  evaporative  efficiency  than  did  the  other  with  horizontal 
return  flue  tubes. 

This  result  can  have  been  due  only  to  the  superior  efficiency 
of  the  water-tube  heating  surface,  as  the  total  quantity  of  fuel 
consumed  and  of  water  evaporated  in  a  given  time  was  greater 
in  the  case  of  the  flue-tube  boiler. 


THE  MODERN  STEAM  BOILER. 


515 


THE  PRACTICAL  PHYSICS  OF 


I  I  I 

I  I  I 

I  I  I 

I  I  I 

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QV      in 

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c?    D>M;><2>S<S  <2V2       H?t?£?2"M'HSHV8' 


fc    S 

t>>        -4-10 


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8*8 


liii 

£  to  H  q 


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1  1 

1    1  1  1  1  1 

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1  1 

1     Mill 

1  1 

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OB  A 


q      qo>qqq    «o    v«ONqootNqq 


o  °M    MO 


HO 


fifi 


CO  CO  CO          <O   O     cots  tN     ts 

MOM  txOO      N   M  M      CO 

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i  i  i 


co  coco    pa  oo  0    o  o 


•Til 

bl  J8  i 


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in  6s  SIS.M 


to.  A 
chim 


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O  tx  00   tx  txoo         2 

OTC/3    W«          wi-      _ 


THE  MODERN  STEAM  BOILER.  517 

S.S.  "  Thetis." — Of  boilers  of  the  water-tube  or  sectional  class 
proper  we  have  many  records  of  trials  and  performances. 

In  1858  a  marine  boiler  of  the  Craddock  design  (with  the 
addition  of  a  steam  dome  and  some  slight  alteration  in  the 
furnaces  and  passages  for  gases,  steam  and  water),  having  nine 
square  feet  of  heating  surface  per  Ib.  of  coal  consumed  per 
hour,  gave  in  the  s.s.  "  Thetis  "  results  which  showed  an  evapo- 
ration of  ii  Ibs.  of  water  per  Ib.  of  coal,  which  had  a  theoretical 
evaporative  power  of  15^,  as  certified  by  the  late  Professor 
Macquorn  Rankine. 

As  a  mean  of  226  indicated  horse  power  per  hour  was 
developed  on  a  consumption  of  roi8  Ib.  coal  per  I.H.P.,  the 
boiler  cannot,  however,  have  had  a  very  active  evaporation  from 
each  square  foot  of  heating  surface.  The  steam  pressure  in  the 
boiler  was  115  Ibs.  per  square  inch. 

Similar  results  at  pressures  from  120  to  150  Ibs.  per  square 
inch  were  obtained  with  sectional  and  water-tube  boilers  of 
Rowan  and  Morton's  design,  during  the  period  from  1859  to 
1874,'  but  the  time  was  not  then  ripe  for  the  employment  in 
marine  practice  of  those  higher  pressures  of  steam  which  make 
this  class  of  boiler  almost  a  necessity,  and  the  use  of  water- 
tube  marine  boilers  was  all  but  discontinued  in  this  country  for 
some  years. 

On  land,  however,  many  different  forms  of  water-tube  boilers 
have  been  systematically  tested  during  that  period. 

American  Trials. — At  the  Fair  of  the  American  Institute  in 
November,  1871,  some  careful  tests  were  carried  out  by  a  com- 
mittee presided  over  by  Professor  R.  H.  Thurston,  who  pub- 
lished the  results  in  a  paper  read  before  the  American  Society 
of  Engineers.2  The  water-tube  boilers  tested  were  those  of 
Root,  Allen,  andPhleger,  and  along  with  these  were  tried  a  Lowe 
boiler  and  a  Blanchard  boiler,  both  being  modifications  of  the 
flue-tube  boiler. 

The  results  are  given  in  the  following  table  : — 


1  See  Trans   Inst.  Engineers  and  Shipbuilders  in  Scotland.     Vol.  xxiii.,  pp. 
51-78,  and  Vol.  xli.,  pp.  29-143. 

2  See    Engineering,    15th   January,    1875,    pp.  49,  50.     Also  "The  Steam 
Engine,"  by  D.  K.  Clark,  Vol.  i.,  pp.  248-252. 


THE  PRACTICAL  PHYSICS  OF 


3  g 

H  a 


•uoipafui 


O  «  m  b  b  a 


O     rOO  00   if 
O  O   O   .-!(- 1- 


35  o  b 


'^9ns         »f  ||  g 


•[EOIJ3J03U.X  *q  psp'Aip  pnj  jo 
uonwodcAa  pmpv    :  Aouapwa 

N    0    0    0  C>  U-; 

N  t^o  «5  tx 
o  o  o  o  o 

•jnou,  J9d  aacjjng  ajrjg 
}OOj  9J«nbs   aad    spunod    '[KO^ 

.  r^iX   f<  **   O 
•-,   t^OC    -    t-  -H 

N  2  «  o  b*  « 

•jnou.  .wd  J9»FA\  J°  ?ooj  otqno 
9uo     ajEJoduAS     o}    pa.unbaj 
aoEjans  SuijcaH  J°  J^J  9JEnbs 

O  w    ^rr;3O 

10  'f  t^^c  f 

si  ro  K  rj  M  rp 

pus  -j 

)0 

-3.mss9.iji  ousqdsounv 

rt-  Q    C^  O    ^f1 
•  vC  >5    rf-  -S-  ro 

>-  b  b  b  b  « 

JOijiuodEAg       }U3iEAinbg 

Actual  Evaporation. 

•9]qi}snq 
-11103    jo     punod      K^ 

.^^R5f;5- 

^  do  do  do  do  CT> 

•IB03  jo  punod  jaj 

^'pr-P°8 

K  K  i>  Koc 

Apparent  Evaporation. 

•jnoij  jad  soBjjns  2ui 
-JE3U,  jo  jooj  9Ji:nbs  jgj 

in  3N  rr,  o  r< 

^   Vg     £?     JH     ^ 

•anOU.  J3d  93BJJHS 

9}BJO  jo  jooj  gjunbs  jsj 

g^^.R^r?, 
»'!8SRR& 

-    -^iqnsnq 

-mo3     jo    punod    jaj 

H-fl-f  ?f 

'l«°3  jo  punod  jg,j 

.S^^rT 

1/3  K  t>  K.  i^do 

•ajqijsnq 
-moo  jo  punod  asd  sjmft  IE}OX 

ff,  N  \O    •*•  't 

to  oo  N  a^ 

«  -JC  rodo  «*• 

«*S  JT?^ 

o"  o"  o"  o"  o" 

•sjiun  IEUU9U.X  MS!1P3  IK1°X 

fcfifo 

T*-|>,  10  CM> 

<*o  cs  00  re  r-H 

.  OC^CO_\O^  I>  IN. 

O*  *-T  t-^^c'oc^  10 
K*   0   N  ^§- 
M"  O"  ro  K  M~ 
m  •*  N  f>  M 

i 

£ 

| 

=    :S3    :.c 

_,  tt/O  w  o 

llsll 

«<^,^S1 

THE  MODERN  STEAM  BOILER.  519 

These  tests  possess  additional  interest  from  their  being 
amongst  the  first  in  which  estimations  of  the  dryness  of  the 
steam  or  amount  of  priming  water  present  were  made  by  the 
calorimetric  method.  For  the  particulars  of  the  method  adopted 
and  of  the  calculations  and  formulae  employed,  Professor 
Thurston's  paper  must  be  consulted.1 

Howard  Boilers. — The  record  of  experiments  on  "  Howard  " 
inclined  tube  boilers,  carried  out  by  a  Committee  at  the  Fair  of 
the  American  Institute  in  1874,  will  be  found  ifl  Engineering  of 
January  26th,  March  2nd,  and  April  i3th,  1877,  pages  80,  176, 
and  226  of  Vol.  xxiii.  It  has  also  features  of  great  interest. 
The  following  is  an  abstract  of  the  principal  results  : — 

ist.  2nd.  Mean. 

Duration  of  experiments 10*5  n 

Pounds  of  fuel  fed  into  furnace  ...  5,ioo 

„       ,,    coal  and  ashes  withdrawn  MSS 


,,       ,,    combustible  consumed...  3,942 

„       „    water  fed  into  boiler    ...17,338        21,015         37,403* 

Less  priming  water...          ...          ...      452          3,ioo  3,552 


Pounds  of  water  evaporated  ...16,886 

Pressure  of  steam  in  boiler  ...     76*5  138*3 

Temperature  of  feed           ...  ...        35°  36° 

atmosphere  ...        35°  45° 

steam  in  drum  114°         346-8°  ^by  ^?*\ 

mometer.) 


„        gas  leaving  boiler        332°         324-2 
,,         ,,    entering  chimney  234 


Pounds  of  combustible  per  hour  ...  J83*5 

„         „           „     sq.  foot  of  grate  6'8 

„  „         „  „         „         „    heating  surface        0-308 

Apparent    evaporation    per    Ib.    of 

combustible      .........  9-024  9*915           9'4^92 

Effective       ...         .........  8798  8-368           8-543 

„       from          212°      ......  !0'75  10*28           10-53 

Percentage  of  total  absorption  (useful)    -742  -709             -726 

1  See  also  Engineering,  Vol.  xiii.,  1872,  pp.  340,  373,  377,  434. 

2  There  is  apparently  some  slight  error  in  these  figures,  as  the  totals  of 
the  water  do  not  agree  in  themselves  or  with  the  rate  of  evaporation. 


520 


THE  PRACTICAL  PHYSICS  OF 


At  the  conclusion  of  the  experiment,  with  the  steam  pressure  at  75  lb.,  the 
safety  valve  was  closed,  and  the  steam  allowed  to  accumulate  in  the  boiler 
until  the  pressure  reached  135  lb. 

During  the  interval  the  fires  were  burning  at  the  same  rate  as  during  the 
other  parts  of  the  experiment. 

The  following  Table  shows  the  increase  of  pressure  : — 


TABLE  LXXI. 


Time. 

Steam. 

Time. 

Steam  . 

hrs.  min. 

hrs.  min. 

5      30 

79 

5    49 

H5 

5    43 

90 

5    50 

118 

5    44 

93 

5    5i 

122 

5    45 

100 

5    52 

125 

5    46 

103 

5    53 

131 

5    47 

105 

5    54 

135 

5    48 

no 

5    55 

blow  off. 

The  boiler  had  been  fed  with  cold  water  just  before  5.30,  and  it  is  believed 
that  the  temperature  of  the  water  in  the  boiler  was  not  uniform  until  5.43, 
after  which  the  increments  of  temperature  appear  to  be  nearly  uniform,  being 
2iLo  deg.  Per  minute. 

The  weight  of  water  in  the  boiler  was  4,400  lb.,  and  the  equivalent  weight 
of  iron  surrounding  it  was  1,200  lb.,  giving  the  total  equivalent  weight  of 
water  to  be  elevated  in  temperature  to  be  5,600  lb.  The  increase  of  the 
temperature  of  the  water  was  from  5-43  to  5'54,  being  n  min.  (358-45 — 331-18=) 
27-25  deg.  The  units  of  heat  corresponding  to  this  elevation  of  the  tempera- 
ture of  the  whole  mass  would  be  (27-25x5600=)  178300. 

This  amount  of  heat  was  transferred  in  n  min.  The  amount  transferred 
during  one  hour,  at  this  rate,  would  have  been  (178300-^11x60=)  861800 
units,  corresponding  to  (861800-^-1156=)  741  lb.  of  steam  from  the  tempera- 
ture of  the  feed. 

But  during  the  interval  immediately  succeeding  the  elevation  of  tempera- 
ture, the  boiler  was  evaporating  (183-5x8-8=)  1615  lb.  of  steam  per  hour.  If 
this  rate  of  transfer  had  continued  during  the  elevation  of  temperature  the 
increment  would  have  been  (2- 1  X  1615-1-741=)  4-4  deg.  per  min.  So  far  as 
this  experiment  goes,  it  would  appear  that  the  heat  was  only  transferred  about 
one-half  as  fast  while  the  pressure  was  rising  as  while  it  was  uniform.1 

If  the  heat  should  be  transferred  during  the  whole  time  while  the  pressure 
was  rising  to  that  pressure  at  which  the  boiler  would  burst,  at  the  same  rate 
as  during  the  elevation  of  pressure  between  the  two  experiments,  the  bursting 
pressure  would  be  reached  in  nearly  23  min.,  for  the  bursting  pressure  of  the 
tube  is  3000  lb.,  and  the  temperature  corresponding  to  3000  lb.  in  797  deg., 

1  Heat  and  Steam  Engine.     Trowbridge,  p.  106. 


THE  MODERN  STEAM  BOILER. 


and  (797 — 320-7-2-1=)  22f  mm.  This  is  about  half  as  long  a  period  as  would 
usually  be  occupied  by  the  ordinary  forms  of  boiler.  The  rapid  variation  of 
pressure  is  the  result  of  the  small  weight  of  water  contained  in  the  boiler. 
This  is  an  important  feature  of  all  the  boilers  of  the  class  to  which  this  belongs.' 
It  must  be  remembered  that  the  cast-iron  heads  will  probably  give  out  at  a  less 
pressure  than  3000  lb.,  although  the  Committee  have  no  means  of  determining 
at  what  pressure  they  will  give  out. 

It  will  be  observed  that  the  temperature  of  the  gas  leaving  the  boiler  is  less 
than  the  temperature  of  the  steam  due  to  the  pressure.  Under  these  circum- 
stances, no  super-heating  is  possible  with  any  super-heater  whatever.  It  will 
also  be  observed  that  at  one  time  the  temperature  of  the  gas  leaving  the  boiler 
is  considerably  hotter  than  the  temperature  due  to  the  pressure  of  the  steam, 
but  the  temperature  indicated  by  the  thermometer  on  the  steam  drum  is  less 
than  the  equivalent  temperature  of  the  steam.  The  following  Table  exhibits 
this  variation  : — 

TABLE  LXXII. 


S 

I 

Differences. 

3 

•    'rt 

2 

</> 

i 

£ 

cB 

*  ' 

c 

Hour. 

s 

6 

H 

"8 

•3   "   -' 

lid 

KJ 

1 

CT1  ^"   ? 

8  3  § 

d 

?i 

J  1 

"rt 

W   «5 

ill 

1 

N 

I* 

1 

«     "o 

|S& 

U> 

£ 

So 

f?: 

S 

S 

<u 
H 

«!-!-•« 

«  B  fa 

0^-2 

H?  1 

9-30 

72 

319 

317-3 

350 

+  32-7 

+  17 

10-00 

73 

311-5 

318-2 

375 

56-8 

-  6-7 

IO-30 

78 

311-5 

322-2 

400 

77-8 

—10-7 

I  TOO 

74 

311-5 

319 

4i5 

94-0 

—  7'5 

II-30 

76 

310-5 

320-6 

390 

69-4 

—  TO'  I 

T2'OO 

75 

310 

319-8 

390 

70-2 

-  9-8 

I2-30 

80 

316 

323-6 

38o 

56-4 

—  7-0 

I  -00 

80 

320 

323-6 

350 

26-4 

-  3-6 

1-30 

77 

311 

321-4 

330 

8-6  (4-57-8) 

—10-4  (—8-) 

2'OO 

80 

319 

323-6 

310 

—22-6 

-  4-6 

2-30 

70 

307 

315-8 

320 

+  4-2 

—  8-8 

3'00 

75 

312 

319-8 

3i5 

-4-8 

-  7-8 

3'30 

79 

318 

322-9 

310 

—12-9 

—  4-9 

4'00 

75 

312 

319-8 

310 

-9-8 

—  7'8 

4'30 

84 

.318 

326-6 

315 

+  ir6 

—  8-6 

5  'oo 

73 

310-5 

318-5 

3i5 

—  3'5 

—  8-0       _ 

5-30 

79 

315 

322-9 

310 

—12-9  —  (10) 

-  7'9  (7-64) 

522  THE  PRACTICAL  PHYSICS  OF 

The  strength  of  the  tubes  of  this  boiler  being  8f  in.  inside  diameter,  and 
yV  in-  thick,  taking  the  strength  of  the  iron  at  50,000  lb.,  and  the  welded  joint 
at  20  per  cent,  less,  will  be 

/•8oxso,ooo       s\ 

—  fj-l  --  X  §  I  =  3000  lb.  nearly  per  sq.  in. 


The  cast-iron  heads  are  probably  not  so  strong  as  the  tubes,  but  the  Com- 
mittee have  no  means  of  determining  how  strong  they  are. 

If  it  is  true,  as  said  by  an  eminent  engineer,  that  "  in  nine  cases  out  of  ten  a 
continuously  increasing  pressure  of  steam  without  means  of  escape,  is  the 
immediate  cause  of  explosion,"  l  the  liability  to  explosion  would  decrease  as 
the  margin  of  strength  increases,  and  this  must  be  looked  upon  as  a  very 
strong  and  safe  boiler. 

There  is  another  point,  however,  which  the  Committee  do  not  feel  justified 
in  passing  without  comment.  The  feed  water  is  introduced  into  all  the  lower 
rows  of  tubes  from  a  common  pipe,  and  these  tubes  are  only  connected  with 
the  steam  space  by  the  back  end.  Now,  it  is  evident  that  if  there  is  any  steam 
formed  in  the  lower  tubes,  it  must  leave  them  by  the  back  end,  and  that  there 
would  be  a  constant  current  of  steam  leaving  the  tubes,  tending  to  carry  the 
water  with  it.  It  is  no  doubt  the  expectation  of  the  builder  that  there  will  not 
be  any  steam  formed  in  the  lower  tubes,  but  that  they  will  only  serve  as  a  feed 
water  heater,  and  that  the  cold  water  pumped  in  at  a  lower  end  will  be 
gradually  forced  along  the  tube  by  the  fresh  supply  of  water  coming  on 
behind  it,  becoming  warmer  and  warmer  as  it  travels  along  the  tube,  but  not 
reaching  the  temperature  of  the  steam  until  it  arrives  at  the  end  and  mixes 
with  the  water  circulating  through  the  upper  tubes.  So  long  as  this  is  the 
case,  no  harm  can  come  from  having  these  tubes  connected  at  one  end  only. 
The  effective  surface  of  the  lower  row  of  tubes  being  one-half  the  total 
surface,  50  square  feet  is  equal  to  (f^=)  1-85  time  the  grate  surface.  From 
experiments  with  other  boilers,  at  the  same  rate  of  combustion,  it  appears 
that  about  6000  units  of  heat  would  be  absorbed  by  this  surface  for  every 
pound  of  combustible  consumed.  During  the  experiment,  the  feed  water  had 
a  temperature  of  35  deg.,  and  each  pound  of  combustible  elevated  9  lb.  of 
water  from  the  temperature  of  the  feed  to  the  steam,  and  evaporated  8'8  lb., 
the  balance,  2  Ibs.,  being  entrained  with  the  steam.  Thus  the  total  heat 
absorbed  was  : 

Water        \  ..................        9x286=2574 

Steam          ..................     8-8x888=7814 

10388 

Therefore  the  units  of  heat  available  to  form  steam  in  the  lower  tube  (6000 
—  2574=)  3426,  and  the  equivalent  weight  of  steam  (3426-1-888=)  3-86.  That 
is  (3-86-^-8.8=)  44  per  cent,  of  the  total  steam  formed  in  the  boiler  will  be 
formed  in  the  lower  tubes.  If  the  water  received  heat  uniformly  from  the 
time  of  its  entrance  during  its  passage  along  the  tube,  it  would  have  acquired 

1  Sir  William  Fairbairn  —  Useful  Information  for  Engineers.  ist  Series, 
p.  58,  Ed.  1864. 


THE  MODERN  STEAM  BOILER. 


523 


the  temperature  of  the  steam  at  (2791-^6000x12=)  $'b  ft.  from  the  front  end 
of  the  tube,  at  this  point  the  steam  would  commence  to  form  and  the  current 
of  water  would  be  reversed.  If  the  combustion  is  slow,  as  in  the  experiment, 
these  two  currents  may  pass  each  other  without  interference,  but  if  the  com- 
bustion be  sufficiently  rapid  so  that  more  heat  is  thrown  on  the  lower  tube 
(see  Fig.  309),  or  if  the  feed  water  enters  the  tube  at  a  higher  temperature  than 
35  deg.,  so  much  steam  may  be  formed  that  the  opposing  currents  of  steam 
and  water  will  interfere  and  drive  the  water  from  the  tube,  when  the  tube 
would  soon  become  red  hot,  and  burst  with  a  very  moderate  pressure. 
Although  it  is  not  probable  that  there  would  be  an  explosion  in  the  ordinary 
acceptation  of  the  term,  still  the  steam  and  water  would  pour  out  into  the 
furnace  with  certainly  disastrous  and  perhaps  fatal  results.  Your  Committee 
cannot  say  at  what  rate  of  combustion  or  temperature  of  feed  steam  would  be 
formed  in  the  lower  tubes  with  sufficient  rapidity  to  expel  the  water.  That 
can  only  be  determined  by  experiment,  but  they  refer  to  the  performance  of  a 
similar  boiler,  the  boilers  of  the  steamship  "  Montana,"  which  would  seem  to 
corroborate  these  views.1  In  the  form  of  boiler  at  present  manufactured  by 
the  exhibitors,  the  tubes  are  connected  at  both  ends,  which  would  obviate  this 
trouble. 


FIG.  309. 


If  there  were  consumed  in  this  boiler  J  Ib.  of  combustible  for  every  square 
foot  of  heating  surface  per  hour,  the  percentage  of  perfect  absorption  would 
be,  computed  as  in  the  other  cases,  62^4  per  cent. 

In  comparing  this  boiler  experiment  with  those  made  under  atmospheric 
pressure,  and  the  ordinary  temperature  (60  deg.),  an  allowance  should  be  made 
for  the  greater  proportion  of  the  heat  necessarily  rejected  through  the 
chimney,  for  the  gas  must  at  best  be  discharged  at  the  temperature  of  the 
steam,  if  there  is  no  feed  water  heater. 

This  allowance  will  be  for  the  Howard  boiler  under  these  circumstances  of 
the  trial  [(335  — 35)-J-(2i2—6o)=]  nearly  2  ;  the  heat  necessarily  wasted  in  the 
ordinary  atmospheric  test,  which  is  [(212  —  6o)-J-(224O— 6o)=]  6'8  per  cent.,, 
and  therefore  in  the  Howard  boiler  (2X6'8=)  I3'6  per  cent. 

That  is,  if  the  Howard  boiler  had  been  tried  under  atmospheric  pressure, 
and  with  an  atmospheric  temperature  of  60  deg.,  the  percentage  of  heat  use 
fully  absorbed  would  have  increased  from  62.4  to  (62.4+6.8=)  69.2. 

The  same  reasoning  applies  to  the  boilers  tested  at  the  Fair  in  1871." 


1  Nautical  Magazine,  London,  November,  1873. 


524  THE  PRACTICAL  PHYSICS  OF 

The  log  of  the  Allen  boiler  is  here  added  for  comparison. 

CALCULATION  OF  THE  LOG  OF  THE  ALLEN  BOILER, 
EXHIBITED  AT  THE  FAIR  OF  THE  AMERICAN  INSTITUTE, 
NOVEMBER,  1871. 

Determination  of  the  heat  carried  away  by  the  condensing  water  discharged 
from  the  tank  during  the  twelve  hours'  trial  : — 

Units. 
To   1.30  p.m.,  1056  cubic  ft.  at  62 \  lb.=66,ooo  Ib.  at  range  of 

1207°  F.         ...         ...         ...          ...         ...         ...         ...         ...      7,966,200 

To  10.30  p.m.,  5480  cubic  ft.  at  62^  ^.=342,500  Ib.  at  range  of 

106-08°  F.      ...         ...         ...         ...         ...         ...         ...         ...    36,332,400 

To  11-35  p.m.,  650  cubic  ft.  at  62^  lb.=4O,625  Ib.  range  of  50-5°  F.      2,051,562-5 


(a)  Total  British  thermal  units       46,350,162-5 


Determination   of   heat   carried  off   by  evaporation  at  the  surface  of   the 
tank  : — 

Units. 
1168-12  Ib.x  1008-8°  (latent  heat  at  152-7°  F.)=(b) ...      1,178,404-5 


Determination  of  heat  carried  away  by  water  of  condensation  : — 

Units. 
39,670  Ib.  at  17-98°  (range=63-48°— 45-50)=(c)       713,266-6 

Total  heat  derived  from  fuel,  as  determined  above  : — 

Thermal  units. 

46,350,162-5+1,178,404-5  +  713,266-6= 48,241,833 

Deduct  4  per  cent,  of  (a)  for  errors  (leakage,  and  meters)  ...       1,854,006-5 


Final  and  corrected  results  ...         ...         ...         ...    46,387,827-1 


British  thermal  units  per  Ib.  combustible,  46,387, 827- 1+4527=10,246-92. 
Equivalent  evaporation  of  water,  temperature  212°  F.,  atmosphere  pressure 
=io,?46-92-J-966-6=io-6o  Ib. 

Apparent  results.  Real  results. 

Water  evaporated  per  Ib.  of  coal  3967°=;-38  39^ZS=7'38 

5375  5375 

Water  evaporated  per  pound  of  combustible  3-96_Z°=876  ^^=^76 

4527  4527 


THE  MODERN  STEAM  BOILER. 


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526  THE  PRACTICAL  PHYSICS  OF 

Philadelphia  Exhibition,  1876. — Of  similar  interest  and  import- 
ance are  the  records  of  tests  of  various  boilers  which  were 
carried  out  at  the  Centennial  Exhibition  at  Philadelphia  in 
1876,  and  at  the  Electrical  Exhibition  held  in  the  same  place 
in  1884. 

The  following  Table  gives  a  summary  of  the  principal  dimen- 
sions of  the  various  boilers  tested  in  1876  : — 


TABLE  LXXV. 

PHILADELPHIA  EXHIBITION,  1876,— SURFACES  AND  VOLUMES  OF  STEAM 
BOILERS  TESTED,  MOSTLY  SECTIONAL. 


Designation  of  Boiler. 

Area  of 
Fire- 
grate. 

Heating  Surface. 

Ratio 
of. 

Water- 
heating 
Surface 
to 
Grate- 
area. 

Volume  of  Boiler. 

Water. 

Steam. 

Total 

Water- 
space. 

Steam- 
space. 

Total. 

Wiegand  . 

sq.  feet. 
'42 
23 
I5-4I 
21 
18.42 
42 
27.50 

30 

22.50 

44-5° 
25 
36 
36 
25 

sq.  feet 
1289.70 
627 
1001.10 

288.04 
MS1-?? 
575-o6 

1005.06 
687.88 
1676.32 
1146.43 

852.54 
630 

sq.  feet. 
49.67 
274 

3° 

218.36 
146.66 

60.48 

557-94 
65.76 

7-57 
487 

sq.  feet 

1339.37 
901 
1031.10 

399-75 
506.40 

1598.43 
63^.54 

1563 
753.64 
1676.32 

"54 
852-54 
"J5 
349-33 

ratio. 
3°-7 
27-3 
64-3 
19.0 

15-6 

34-6 
20.9 

33-5 
30.6 

37-7 
45-8 
23-7 
17-5 
14.0 

cu.  feet. 
181.36 

54-09 
145.12 

36-I5 
80.74 
116.68 

58.17 

83.77 
I40.I8 
229 
136.12 
562.91 
66.90 
20.11 

cu.  feet. 
44.18 
23.72 
92.20 
24.85 
25-45 
45-69 
27.97 

44.60 
50.9P 
137.85 
127.39 
169.12 

55-75 
43-  ri 

cu.  feet. 

225.54 
77.81 
237.32 

61.00 
106.19 
162.37 

86.14 

128.37 
191.08 
366.85 
263.51 
732-03 
122.65 
63.22 

Harrison      

Firmenich  

Rogers  and  Black  
Andrews    

Root  

Kelly  (including  }i  ) 
of  water-heater)    / 
Exeter 

Lowe 

Babcock  and  Wilcox 
Smith 

Galloway  .    ... 

Anderson  

Pierce 

The  results  obtained  in  these  trials  have  been  published  with 
some  slight  variations  by  the  makers  of  certain  of  the  boilers,  but 
the  following  Table  gives  those  accepted  by  the  late  D.  K. 
Clark  as  an  impartial  judge  in  the  matter  : — 


THE  MODERN  STEAM  BOILER. 


527 


Sll 


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snouiuinjiq 
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includi 


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ting  of  steam... 
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eaving  the  boile 


,  rf^^i^vlll 


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ex,     wH 


These  trials  are  arranged  under  the  two  heads  of  "  capacity" 
and  "  economy  "  ;  "  capacity  "  being  taken  as  the  quantity  of 
water  evaporated  per  hour  or  evaporative  power,  and  "economy" 


528 


THE  PRACTICAL  PHYSICS  OF 


W 


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tri 

DESIGNATION  OF  BOILER  -1 

I.  Coal  consumed  per  hour.i 

including  equivalent  of  |-pounds. 

2.  Coal  consumed  per  hour\ 
per  sq.  ft.  of  fire-grate..  / 
3.  Refuse  per  hour  , 
4.  Do.  percent  p.  cent. 
5.  Combustible  per  hour...  pounds. 
6.  Do.  do.  per  sq.  foot  of  j 
fire-grate  /  " 

7.  Temper,  of  feed-water.  .  .  .  Fahr.  * 
8.  Water  consumed  per  hr.,\  cu  ftet 
apparently  evaporated; 

9.  Water  evaporated  per  \ 

Ihour,  corrected  for  j-  ,, 
quality  of  steam  ) 

IO.  Uo.  do.  do.  per  square  \ 
foot  of  fire-grate  ) 
II.  Do.  per  pound  of  coal...  pounds. 
12.  Do.  per  pound  of  coal,\ 
from  and  at  212°  F  /  " 

°  i 

c    : 

u  2 

TJ 

C 
rt 

O 
°N 

15.  Priming,  or  moisture  in\ 
steam  /p  c 
16.  Superheating  of  steam...  degs.  F. 

117.  Temperature  of  burnt)  . 
gases  leaving  the  boiler  J  a 

as  quantity  of  water  evaporated  per  pound  of  fuel  under  ordinary 
working  conditions.  A  comparative  view  of  the  performances 
of  these  various  boilers  is  afforded  by  Table  LXXVI.  : — 


THE  MODERN  STEAM  BOILER. 


529 


cal  shell,  multitubular  flue  — 
underfiring. 
cal  shell,  furnace  tubes  and  w 
cal  shell,  multitubular  flue  ;  u 


Cylind 
flues 
Cylind 
Cylind 


II  I 

^o  2 

3o  °«n 

•a  °  ~ 

S*  1 

>>  c  ~ 


n 
i 


-inch  water-tu 
-inch  water-tu 
draught. 
/^-inch  water-tu 
drauht. 


fliijll 

a  G  s?    .  o  $J  JS 


st-iro 
eres, 


cylinder,  with  fl 
double  return  mul 
arly  horizontal;  re 
boiler,  with  extern 
ertical,  with  interna 
slightly  inclined  ; 
m  to  promote  circu 


II 


vo     q 

co'     N* 


q  q       w 
*J  4o.  M 


OO        I^VO 

uS    to  d 


vo     to      OvomOt^      ON 
tO      £-      ^^^S'0'       O* 


!« 

JS 


co     in  q 

d    co'  o 


CO          M 

d    co 


fO      to      M    N  CO  CO    N      CO 
CO         l-«        ti.  t^OO    ti.   M         ON 


ON     ON 
i-<        N 


N    *f  N    tn    to      M 

q  q  vq  vq  oo     to 
d  w  d  o\  d     d 


W! 
4K- 


tO        M  TJ- 


rj-     Tj-    in  to  to  t^-vq     ON 

N         VO*          ONtHtOMTJ-         T$- 


SO       •*         to 

o     •<*•      to 

M          d  d 


0\CO      OO 
ON     ON     O 


•s      g 

' 


Some  figures  enabling  a  comparison  to  be  made  between 
these  and  the  Howard  boilers  already  referred  to,  will  be  found 
in  Engineering, iVol  xxiii.,  p.  176. 


530 


THE  PRACTICAL  PHYSICS  OF 


The  following  diagram,  Fig.  310  (published  in  the  1884  edition 
of  Steam  by  the  Babcock  and  Wilcox  Company)  exhibits  the 
effects  of  comparing  these  various  boiler  trials  in  respect  of  several 
elements  : — 


Po^ndd  of  W.t. 
from  and  at  211 

pound 
combustible 
m   -MG 


•^ Llrfe  of  thW 

9 


Ecor 


~ISTb«  WitrrperTL  of  Combustible. 

Ill  I 


COAL 

butned  per  hour 
>er.  sq.  ft.  grate 
mm  .  Mb. 


RATIO 

icsting  eurfare 
,o  •grate  eurlace 
mm.  .1. 

WATER 

per  en  ft  .of 
heatlDK  siirlAce 
per.  hour. 
imni.-=Ub. 


WASTE 

heatofnae 
inim.  =SO'?. 


FIG.   310. 


The  following  remarks  accompanied  this  diagram  : — 

"  Entirely  independent  of  the  question,  which  boiler  is  the  best  for  use  ? 
there  is  an  inquiry  of  great  interest  in  a  scientific  point  of  view,  and  that  is 
What  elements  in  the  construction  or  arrangement  of  the  boilers  tested  con- 
tributed to  the  difference  in  results  ?  Not  enough  data  are  given  to  enable  us 
to  solve  this  problem  ;  but  to  show  what,  if  any,  effect  certain  elements 
produced,  we  have  constructed  the  annexed  diagram.  The  height  of  the  dia- 
gram is  15  centimeters,  and  represents  the  theoretic  value  of  the  combustible 


THE  MODERN  STEAM  BOILER.  531 

used  in  the  experiments.  In  the  line  of  "  economy  "  the  boilers  are  arranged 
in  the  order  of  their  relative  economy,  as  shown  in  the  Table.  The  distance 
of  this  line  from  the  base,  relative  to  the  whole  height,  gives  the  percentage 
of  useful  effect  in  each  case,  and  it  is  the  relation  of  the  other  lines  to  this 
that  we  have  to  study. 

"  If  we  examine  the  line  representing  the  evaporation  per  square  'foot  of 
surface,  we  are  struck  at  once  by  the  fact  that  it  bears  no  relation  whatever 
to  the  line  of  economy.  Now,  we  know  that  in  any  given  boiler,  this  fre- 
quently has  a  marked  effect  in  that  respect  ;  other  things  being  equal,  the 
slower  the  rate  of  evaporation  per  square  foot,  within  certain  limits,  the 
higher  the  economical  results.  .But.  as  the  value  of  the  heating  surface  under 
differing  arrangements  varies  in  a  much  greater  ratio  than  the  effect  of 
forcing  a  given  surface,  as  our  diagram  shows,  no  general  rule  can  be  made 
to  apply.  The  same  remarks  will  apply  to  the  lines  representing  the  rate  of 
combustion  per  square  foot  of  grate,  and  the  ratio  of  heating  surface  to  grate 
surface.  These  latter  must  have  a  conjoined  relation  to  the  rate  of  evapora- 
tion, modified  also  by  the  quality  of  the  heating  surface  ;  but  for  the  same 
reason  above  given,  no  general  relation  exists  between  them  and  the  econom- 
ical effect  in  different  boilers.  To  show  this  more  perfectly,  we  have  drawn 
an  average  line  in  each  case  (not  including  the  very  erratic  results  of  the 
Pierce  boiler,  for  reasons  above  given),  and  it  will  be  seen  thereby,  that  boilers 
at  the  extremes  of  economy  had  an  average  of  each  of  these  conditions. 
The  different  results  are,  therefore,  to  be  attributed  to  difference  in  the  con- 
struction of  the  boilers,  by  which  the  heating  surface  was  rendered  more 
effective.  The  fact  that  the  best  economic  results  were  obtained  by  a  boiler 
under  average  conditions  in  other  respects,  is  significant,  and  shows  that 
more  is  to  be  hoped  for  through  improved  construction  and  arrangement, 
than  from  extremes  in  proportion. 

"  The  line  representing  the  heat  in  flue,  as  was  to  be  expected,  bears  a 
general  ratio  to  the  total  losses,  though  not  directly  in  each  individual  case. 
This  line  is  probably  too  low  in  every  case,  as  it  undoubtedly  is  in  several, 
where  the  temperature  in  the  flue  is  given  as  lower  than  that  of  the  steam, 
which  could  only  result  from  the  leakage  of  air  into  the  flue.  As  it  is  not  to  be 
supposed  that  such  an  error  could  have  been  permitted,  the  discrepancy  is 
probably  chargeable  to  the  pyrometer  used." 

It  is,  however,  quite  possible  to  read  this  diagram  in  another 
light. 

Philadelphia  Electrical  Exhibition,  1884. — At  the  International 
Electrical  Exhibition  at  Philadelphia  in  1884,  trials  of  two 
sectional  or  water-tube  boilers,  viz  :  the  Root  and  the  Harrison, 
and  two  shell  or  multitubular  flue-tube  boilers,  viz  :  the  Dickson 
and  the  Baldwin,  were  carried  out. 

Table  LXXVII  gives  the  principal  dimensions  of  these 
boilers  : — 


THE  PRACTICAL  PHYSICS  OF 


TABLE  LXXVIL— INTERNATIONAL  ELECTRICAL  EXHIBITION,  1884. — SURFACES 
AND  VOLUMES  OF  STEAM  BOILERS  TESTED  :  SECTIONAL  AND  MULTITUBULAR. 


Designation  of  Boiler. 

Root. 

Harrison. 

Dickson. 

Baldwin. 

Nominal  horse-power,  rated  by  makers...  H.  P. 
Water-heating  surface.  .                ..            so  ft 

150 

I44O 

TOO 

048  c. 

76 
841 

50 

667,    7 

Steam-heating  surface 

760 

2  ? 

I  7.6   7. 

Total  heating  surface 

1800 

I2Q7  C, 

847  c 

7QQ  6 

Grate-area  .            .  .     , 

CQ 

7C.I7, 

7,1.41 

21 

•Ratio  of  grate-area  to  heating  surface  
Heating  surface  per  horse-power               so  ft 

i  to  36 

12 

i  to  37 

17 

i  to  26.8 

II.  I 

11038 

16 

Grate-area  per  horse-power  ,  , 

,ej 

.7C 

.41 

.42 

Height  of  chimney  above  level  of  grate....  feet 
Steam-room  in  boiler   cu  ft 

44-5 
7.6<c 

44-5 

20.8 

28.6 
67 

44-5 

The  principal  results  of  the  performance  of  these  boilers  are 
given  in  Table  LXXVIII  :— 

TABLE  LXXVIII.— INTERNATIONAL  ELECTRICAL  EXHIBITION,  1884  :— 
COMPARATIVE  PERFORMANCE  OF  STEAM  BOILERS. 


Designation  of  Boiler. 

Root. 

Harrison. 

Dickson. 

Baldwin. 

Duration  of  trial                                               hours 

7.6 

7.6 

7.6 

24 

Coal  consumed  per  hour,  including  equi-    1           , 
valent  of  wood                                          f  P° 

502-5 

328.0 

558.0 

253-2 

Do.           do.         per  sq.  ft.  of  fire-grate.      „ 
Refuse  per  hour 

10.05 

74 

9-3 
41 

I7.8 
I4O 

12.0 
27 

Do      percent  p.  cent 

14  7 

I2.q 

2  C  O 

IO  7 

Combustible  per  hour                                     pounds 

428  Z 

'••3 

287  o 

226  2 

Do.              do.       per  square  foot  of    I 
grate1  1       " 

8.6 

8.2 

13-3 

10.8 

Temperature  of  feed-water  Fahr. 
Water  evaporated  per  hour  cub.  ft. 
Water  evaporated  per  hour  per  sq.  ft.  of    ( 
fire-grate  f       " 
Water  evaporated  per  pound  of  coal             pounds 

7i°.6 
60.06 

1.20 
7  4<i 

68°.  8 
41.22 

1.17 

7  84 

67°.2 

61.06 
1.94 
6  ST. 

59°-9 

25-45 

I.  21 

6  27 

Water  evaporated  per  pound  of  coal,  from  1 
and  at  212°  F                                           j      " 

8.79 

9-25 

8.06 

7.40 

Water  evaporated  per  pound  of  combus-  ) 
tible                     ..                                  J      " 

8-75 

8.96 

9.12 

7.02 

Water  evaporated  per  pound  of  combus-  ) 
tible  from  and  at2i2°F.            ..           f      " 

10.32 

10-57 

10.76 

8.28 

Priming,  or  moisture  in  steam  p.  cent 
Superheating  of  steam...                                 degs  F 

2°  2 

i-SS 

7°  O 

Temperature  of  burnt  gases  in  chimney  Fahr. 
Effective  steam-pressure  per  square  inch  Ibs. 
Barometer  inches 

Draught  in  chimney 

370° 
91.4 

30.3 

i     '7 

411° 

95-8 
3°-3 

.24 

423° 
83-5 
3°-3 

•15 

347° 
98.7 

3°-3 
•43 

Temperature  of  the  air  .                                 Fahr 

1  blower 

"c8°a 

steam  jet 
5°° 

natural 
AC° 

(Ibs. 
Air  consumed  per  pound  of  coal             <    cwb  ft 

22.29 
) 

20.06 

.18.74 

20.24 

(at62aF. 

}293 

264 

246 

266 

THK  MODERN  STEAM  BOILER. 


533 


FIcU 7/tr's  Trials. — To  conclude  this  survey  of  trials  of  land 
water-tube  boilers,  we  add  the  results  of  comparative  trials  of  a 
Sinclair  boiler  and  a  Lancashire  boiler  as  carried  out  by  Mr. 
Lavington  E.  Fletcher.1  The  Sinclair  boiler  was  of  75  nominal 
horse  power,  and  was  composed  of  115  water-tubes  of  lift.  9  ins. 
long  and  4  inches  diameter.  The  Lancashire  boiler  was  25ft. 
3  ins.  long,  and  7  feet  in  diameter,  with  two  furnace  tubes 
2  ft.  9  ins.  in  diameter.  The  respective  areas  were  : 


Grate  area 
Heating  surface 
Ratio  of  above 


Sinclair.         Lancashire. 
39-5  sq.  ft.          36*6  sq.  ft. 
1507-0     „  698-5       „ 

i  to  38-1     ,,'     i  to  19-1       „ 


The  boilers  were   fed  with   cold  water,  and  the  leading  results 
were  as  follows  : — 


TABLE  LXXIX. 
SINCLAIR  AND  LANCASHIRE  BOILERS  : — COMPARATIVE  TRIALS. 


Designation  of  Boiler. 

Sinclair. 

Lancashire. 

Lancashire. 

Duration  of  trial                   

7  hours 

7  hours 

4^2  hours 

Pressure  of  steam  in  boiler 

30  Ibs.  to  3  5  Ibs. 

3  5  Ibs.  to  40  Ibs. 

30  Ibs  to  3  5  Ibs. 

Coal  consumed  per  hour  < 

5.86  cwt.  = 
656  Ibs. 

7.57  cwt.  = 
848  Ibs. 

7.45  cwt.  = 
833.7  Ibs. 

Do.         do.        per  sq.  foot  of  grate... 

16.6    „ 

23-17   » 

22.77    „ 

Temperature  of  feed-water  

88°.  8 

80°.  6 

85°.  2 

Water  evaporated  per  hour  

75.90  cu.  ft. 

78.76  cu.  ft. 

78.20  cu.  ft. 

Do.          do.         per  sq.  foot  of  grate 

1.92     „ 

2.15      » 

2.14     „ 

Do.          do.         per  pound  of  coal... 

7.23  Ibs. 

5.80  Ibs. 

5.86  Ibs. 

Do.          do.         from  ?ind  at  212°  F. 

8.31    „ 

6.67    „ 

'6.74  „ 

Temperature  in  flue,  beyond  damper 

450°  F.    { 

800°  and  up- 
wards 

800°  and  up- 
wards 

Coinparalii'c  Space  Occupied. — A jough  comparison  of  the  space 
occupied  by  various  types  of  land  boilers  is  afforded  by  the 
following  tabular  statement,  published  by  J.  H.  Ashby  in  a  paper 
on  water-tube  boilers  in  Proc.  Cleveland  Inst.  of  Engineers 
(3rd  October,  1898)  :— 


1  Sec  "  The  Engineer"  24  August,  1877,  p.  129. 

Reports   of    the    Manchester    Steam    Users    Association,    November   and 
December,  1877. 

Also  -The  Steam  Knj^ine,"  by  D.  K.  Clark,  Vol.  i,  p.  274. 


534 


THE  PRACTICAL  PHYSICS  OF 
TABLE  LXXX. 


Type  of  boiler. 

Sizes. 

Space  occupied  over 
setting  with  combus- 
tion chamber. 

Mean 
evaporation 
per  hour. 

Lancashire  with  three 
flues 

36ft.by8ft.6in. 
diameter 

46  ft.  by  13ft. 

8-00 

Lancashire    with    two 
flues 

30  ft.  by  8  ft. 
diameter 

40  ft.  by  12  ft. 
6  ins. 

6-50 

Egg-ended 

60  ft.  by  4ft. 
diameter 

62  ft.  by  8  ft. 

2-50 

Babcock  and  Wilcox 

2852  sq.  feet 
heating  surface. 

32ft.  by  10  ft. 
10  ins. 

13-00 

Donkin's  Experiments. — A  summary  of  twenty-one  experiments 
was  published  by  Mr.  Bryan  Donkin  in  Engineering  (20  Sept., 
1895),  Vol.  Ix.  p.  347. 

The  following  tables  give  particulars  of  the  dimensions  of  the 
boilers,  and  of  the  results  of  the  various  trials. 


THE  MODERN  STEAM  BOILER. 


535 


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THE  PRACTICAL  PHYSICS  OF 


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THE  MODERN  STEAM  BOILER. 


537 


TABLE  LXXXIII. 

ANALYSES   OF   AND    CALCULATIONS    CONNECTED    WITH 
FURNACE    GASES,    &c. 


E<  perimeiit  Number     .. 

'• 

II. 

III 

IV. 

V. 

VI. 

VII. 

V. 

Analysis  of  Dry  Furnace 
Oases. 

3 

1 

1 

I 

1  i 

i 

i 

1 

* 

1 

I 

j 

i 

[U 

1.  Percent»geof  COS  )  0- 
*.            „              CO   (  d. 

4°:     ::       2ji 

10.33 

2.77 
6.07 

80.83 

15.16 
2.59 
6.46 
7680 

13.00 
000 
11.16 
76.86 

18.21 
0.24 
7.66 
74.00 

11.71 
0.00 
13.13 
75.16 

7.90 
0.00 
17.00 
76.10 

7.  Itl  10.  44 
029      028 
12.61  1  13.37 

bO  1)8  !  75.90 

7.44 
0.10 
12.34 
tO.  12 

11.00 
013 

13.20 
76.70 

10.231  14.  i5 
0.301    r.28 
7.8CJ    .    .1 
81.'(  J    1C.  46 

5.  Pounds  of  dry  air  per 

pound  of  C      ..         ..:        18.5 

27.6 

19.2 

so 

7 

46.0 

sa 

1 

323 

233 

6.  Pounds  of  dry  (line  5  \ 
air  per  pound  4      x       V-   16.4 
of  coal           ..  (  0.886  ') 

24.4 

17.0 

27.2 

40.7 

29.8 

28.6 

ri 

7.  Pounds  of  diy  air  per 

pound  of  pure  and  dry 
Joal       ..        ..        ..         16.9 

26.S 

17.6 

28.0 

42.2 

80.3 

293 

21.1.1 

8.  Pounds  of  dry  furnace 

gases    ditto   (not   in- 

cluding HaO)  .. 

17.6 

26.8 

18.1 

28 

6 

42.8 

80 

9 

80.2 

21  *»*) 

9.  Ratio  of  air  used  to  air' 

theoretically  required 

1  (8 

2.40 

1.63 

2.61 

4.28 

282 

279                1  ;•» 

Experiment  TJcnibcr    .  . 

IX. 

XI. 

x;i.             xui. 

XIV. 

XVIL 

XfX.       '         K 

Analysis  of  Dry  Furnace 
Gaaea. 

| 

V 

1 

•5 

1 

1 

I 

1 

Volume. 

I 

§ 

1 

„.     1    ^ 

j 

i 

i.  Percentage  of  COj">  d 
t.         „              CO    IB 

!:    ::      5  II 

5.  Pounds  of  dry  air  pel 

6.77 
0.00 
13.37 
80.86 

8.60 
0.00 
14.40 
77.00 

11.34 
O.J3 
733 
81.10 

16.10 
0.21 
7.76 
75.53 

H).30 
0.00 
8.30 
81.40 

16.10 
000 
8.80 
7610 

12.40 
1  10 
020 
80.80 

17.94 
1.02 
653 
7461 

11.20 
0.00 
7>0 
81.00 

1490 
0.00 
660 
7860 

7.60 
0.00 
12.18 
80.32 

11.10 
0.00 
13.10 
7560 

11.53 
0.10 
13.03 
7i.44 

13.00 
037 
5.64 
8109 

pound  of  C     .. 
6.  Pounds  of  dry    line  5 

42.1 

21.2 

237 

18.2 

21.0 

3t7 

81.2 

18 

air  per  pound  <     x 

}     87.8 

li 

.S 

21.0 

1 

1.1 

2] 

.8 

£30 

£ 

.6 

16 

cf  coal  .  .         I  0.886 

7.  Pounds  of  dry  air  pel 

pound    of    pure   and 

dry  coal 

38.6 

1 

.4 

21.7                  1< 

.7 

£! 

-0 

SO.O 

2 

1  0 

1ft 

8.  Pounds  of  dry  furnaoi 

gases    ditto  (not    in- 

cluding H^O)  .. 

39.2 

2( 

.0 

228 

r 

.3 

25 

6 

30.6 

| 

>  2 

17 

9.  Rktioof  air  used  toai< 

theoretically  rtquirtc 

8.6 

1.81 

2.0]        ;            1.66 

2.06 

2.SO 

2.67 

U 

538 


THE  PRACTICAL  PHYSICS  OF 


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Experiment  Number  .. 

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Total 
Loos  by  heating  fur- 
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from  action  of  eoono- 
miser 

THE  MODERN  STEAM  BOILER. 


539 


These  results  were  plotted  in  a  diagram  giving  a  graphic 
representation  of  them  arranged  in  the  order  of  the  thermal 
efficiencies  yielded  by  the  trials.  Three  locomotive  trials  were, 
however,  treated  separately  on  account  of  the  conclusion  that 
some  priming  had  taken  place  in  their  case. 

The  following  Fig.  311  is  a  reproduction  of  the  diagram  : — 


FIG.  311. 


54°  THE  PRACTICAL  PHYSICS  OF 

Marine  Boilers. — In  the  early  days  of  the  introduction  of  steam 
of  high  pressure,  generated  in  sectional  or  water-tube  boilers, 
into  steamships,  the  performance  of  the  boilers  was  not  noted 
separately,  the  main  point  of  observation  having  been  the 
quantity  of  coal  consumed  for  the  power  developed  by  both 
boilers  and  engines.  Consequently  there  is  only  a  meagre 
supply  of  details  available  in  the  case  of  the  boilers  which 
were  used.  Published  details  of  the  engines  are  much  more 
complete. 

Rowan  and  Horton  Boilers. — Table  LXXXVI  contains  some 
particulars  of  the  working  of  Rowan  and  Horton  boilers,  of  both 
cellular  and  water-tube  designs,  during  a  period  from  the  year 
1858  to  1874.  Of  some  other  examples  no  record  whatever  has 
been  kept. 

The  S.S.  "  Actif,"  which  was  a  dispatch  boat  of  the  French 
Navy,  was  fitted  in  1869  with  the  early  form  of  Belleville  boilers, 
to  replace  those  of  Rowan  and  Horton,  the  original  engines 
remaining. 

The  boiler  of  the  S.S.  "  Thetis "  was  of  Craddock's  design, 
modified  to  some  extent  by  Rowan  and  Horton  ;  those  of  the 
other  vessels,  down  to  and  including  the  S.S.  "  Actif,"  were  of 
Rowan  and  Horton's  cellular  design,  whilst  those  of  the 
'•'  Haco,"  "  Propontis,"  "  Nepaul,"  and  "  Bengal,"  were  of  the 
Rowan  and  Horton  water-tube  form,  as  also  were  the  second 
sets  of  boilers  fitted  in  the  steamers  u  Punjaub,"  "  Oude,"  and 
"  Burmah,"  in  1873-74.  The  cellular  boilers  were  also  fitted 
in  the  steamers  "  Progress "  and  "  Ballina,"  and  the  S.S. 
"  Western,"  these  having  been,  like  most  of  the  others,  con- 
structed by  Messrs.  R.  Stephenson  and  Co.,  of  Newcastle-on- 
Tyne. 

Although  in  all  these  steamers  the  power  was  produced  with 
what  was  in  those  days  a  startling  economy  of  fuel,  and  at 
a  rate  of  combustion  per  I.H.P.  not  surpassed  as  yet, nevertheless 
the  conditions  of  slow  combustion  under  which  the  boilers  were 
worked,  made  it  necessary  to  have  a  large  amount  of  heating 
surface,  the  unit  of  which  consequently  did  not  showT  a  high 
evaporative  efficiency. 


THE  MODERN  STEAM   BOILER. 

TABLE  LXXXVI. 


ROWAN     AND     HORTON     BOILERS. 


Name  of  Vessel. 

Pressure 
of  steam 
Ibs.  per 
sq.  in. 

Total  heat 
ing  surface 
sq.  feet. 

Grate 

area  sq. 
feet 

Con- 
sum  pt'n 
of  coal 
p.I.H.P 
hour  Ibs 

Date  of  trials. 

S.S.  Thetis      

H5 

1923-15 

36 

roi 

Nov.  20,  1858. 

»             )> 

90 

— 

— 

I'2O 

Aug.  12,  1859. 

»             » 

— 

— 

— 

I-70 

Mean  of  14  voyages, 

May  14  to  Aug.  25, 

1859. 

S.S.  Queen  of  the  Isles 

98 

880 

19-44 

1-74 

Sept.  29,  ib6o. 

S.  Guajara 

102 

2752 

50 

I-50 

Jan.  15,  1861. 

S.  Diamantina 

111-5 

1650 

24 

I-42 

Jan.  22,  1861. 

>)             H 

105 

— 

— 

r86 

Coal  includes  laying 

fires  April  17  to  26, 

1862. 

»             » 

120 

— 

— 

1-23 

Jan.  30,  1861. 

%}    S.S.  Sicilia      

I2O 

r6 

July,  1861. 

!           "       " 

H5 

1-36 

Aug.  15,  1  86  1. 

?'    S.S.  Italia        

120 

II35'6 

48 

i'5 

Dec.  30,  1861. 

y\    S.  Punjaub 
l>  S.  Oude           

120 
120 

3960 

66 

.7    { 

Mean  of  22  trials, 
from   June     13     to 

f  /    S.  Burmah      

I2O 

I 

Aug.  30,  1861. 

S.S.  Actif        

I2O 

3740 

62 

1-6 

Feb.,  1862. 

S.S.  Haco        

150 

1805-5 

1-7 

Oct.,  1870. 

S.S.  Propontis 

J3I-4 

8700 

121-6 

1-6 

Mean  of  63  obser- 

vations, April  7  &  8, 

1874. 

n             " 

I32-9 

— 

— 

1-64 

Average  of  voyages, 

June  30  to  July  16, 

1874. 

More  Recent  Trials, — The  following  Tables  contain  records  of 
trials  of  various  marine  water-tube  boilers  of  later  date,  and 
they  explain  themselves. 


542 


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U.S.S.  "  CushinK." 

THE  MODERN  STEAM  BOILER. 


543 


TABLE  LXXXVIII. 

Boilers   in   preceding   Table   with  Thornycroft    boiler   of    Torpedo    boat 
Ariete"  added.     Arranged  by  Engineer  R.  S.  Giffen,  U.S.N. 


i 

2 

3 

4 

5 

Boilers. 

Combustible 
aer  sq.  feet  of 
heating 
surface. 

Evaporation 
per  Ib. 
combustible. 

Heating  sur- 
face per 
cubic  foot. 

Weight  per 
sq.  ft.  heating 
surface. 

1x2x3 

4 

Ward  (Launch)  ... 

•159 

1077 

3'4I3 

13-2 

'443 

Towne 

•IQO 

13-40 

3'694 

21-8 

•431 

Herreshoff 

•301 

10-23 

2-945 

I4-8 

•613 

Ward  (Launch)  ... 

•323 

lO'OI 

3-4I3 

13-2 

•836 

Belleville         ^  ... 

•501 

10-42 

1-228 

53-2 

•120 

Thornycroft 

•823 

IO-83 

2-180 

I0'2 

1-905 

Scotch 

•870 

9'93 

1-268 

41-2 

•266 

Herreshoff 

•930 

8-68 

2-945 

I4-8 

I  '606 

Ward  (Large)     ... 

1-122 

8-44 

3-39I 

I2'3 

2-6I5 

Towne 

I-I48 

6-77 

3-694 

21-8 

I-3I7 

Scotch 

I-4I5 

9-06 

1-268 

41-2 

•395 

Ward  (Launch)  ... 

1-427 

7-01 

3-4I3 

13-2 

2-586 

Locomotive 

2-220 

774 

1-771 

31-3 

•978 

Locomotive 

2-728 

7'35 

1-771 

31-3 

ri34 

TABLE  LXXXIX. 

MARINE    BOILERS. 

Ward  and  Scotch  boilers  in  "  Monterey"  and  navy  tugs. 


Weight. 

Grate  Surface. 

Heating  Surface. 

l.H.P. 

Speed  of  Vessel. 

Scotch... 

90,040  Ibs. 

88  sq.  ft. 

2,840  sq.  ft. 

373 

11-14  knots. 

Ward  ... 

34,720  Ibs. 

308  sq.  ft. 

1  1,  880  sq.ft. 

524 

13-1     knots. 

544  THE  PRACTICAL  PHYSICS  OF 

The  tests  referred  to  in  the  next  table  were  carried  out  by 
Engineers  of  the  United  States  Navy,  who  had  the  opportunity 
of  testing  the  two  systems  of  boilers  under  fairly  similar 
conditions. 

Preliminary  tests  were  first  made  on  a  boiler  which  had  been  in  use  for 
several  years  at  the  company's  works  at  Elizabethport,  New  Jersey,  with  the 
boiler  burning  5olb.  of  coal  per  square  foot  of  grate  area.  This  boiler 
occupied  an  area  on  floor  of  lo^ft.  by  8ft.,  the  height  being  i2ft.  lof  in.,  and 
with  heater  i5ft.  7in.  The  total  grate  area  was  38^  square  feet,  heating 
sutface  1337^  square  feet,  excluding  215  square  feet  in  the  feed  water  heater. 
The  weight  of  the  boiler  was  39,8i81b.,  and  with  water  it  was  49,257^.,  equal 
to  3i'7lb.  per  square  foot  of  heating  surface,  and  1279-4^.  Per  square  foot  of 
grate  area. 

The  pressure  of  steam  was  I7ilb.,  the  air  pressure  in  ashpit  equal  to  '889!^, 
at  the  base  of  smoke  pipe  '54ilb.,  and  in  furnace  -i681b.,  the  draft  being 
forced  by  a  steam  jet  at  the  base  of  the  smoke  pipe  and  by  a  Sturtevant  fan. 
The  actual  rate  of  combustion  was  44'i661b.  of  fuel  per  square  foot  of  grate, 
but  allowing  for  the  dry  refuse  from  the  ashpit,  4i'O77lb.  per  square  foot,  the 
evaporation  from  and  at  212  degrees  being  8'472lb.  per  Ib.  of  actual  fuel,  or 
9'i09lb.  per  Ib.  of  net  "  combustible."  After  the  test  was  completed  the  fires 
were  drawn  and  the  water  blown  out.  Two  workmen  with  two  helpers  then 
split  both  ends  of  a  lower  tube,  drew  it  out,  put  in  a  new  one,  expanded  it, 
and  replaced  the  caps  ready  for  water  in  22^  minutes.  The  internal  surface 
was  clean,  but  there  was  a  considerable  quantity  of  soot  baked  on  the 
outside.  There  was  no  cleaning  or  sweeping  during  the  trial,  and  after  the 
24  hours'  run  2361b.  of  soot  were  removed  by  a  steam  jet. 

The  trials  on  ship-board  are  still  more  significant,  since  comparison  is 
afforded  with  Scotch  boilers.  The  American  Lake  steamers  "  Zenith  City  " 
and  the  "Victory"  are  4Ooft.  long  over  all,  and  at  i6ft.  draught  displace 
6617-9  tons.  They  have  triple-expansion  engines,  the  "Victory"  having 
cylinders  23in.,  38in.,  and  63in.  diameter  by  4Oin.  stroke.  The  high-pressure 
cylinder  of  the  "  Zenith  City"  is  lin.  less,  to  compensate  for  higher  steam 
pressure— that  is  the  only  difference  in  machinery.  But  the  "  Zenith  City  " 
has  two  Babcock  &  Wilcox  water-tube  boilers  ;  the  "  Victory  "  two  Scotch 
boilers.  The  grate  surface  of  the  former  is  134  square  feet,  of  the  latter  144  ; 
the  heating  surface  being  respectively  6800  and  5715  square  feet.  Thus  the 
ratio  of  heating  surface  to  grate  area  is  in  the  water-tube  boilers  507  to  i, 
and  in  the  multitubular  boilers  39-6  to  i.  The  total  weight  in  steaming 
condition  is  in  the  case  of  the  water-tube  boiler  173,876^.,  in  the  other 
335,787lb. — nearly  double — so  that  the  weight  per  square  foot  of  heating 
surface  is  25-57^.  to  587lb.  in  the  old  type.  Now  for  results,  the  water-tube 
boiler  figures  being  given  first  in  each  case.  The  average  horse-power 
developed  on  the  run,  24  hours  in  the  one  case  against  9^  hours  in  the  other, 
was  I54O'I9  against  1438-8  I.H.P.,  which  is  equal  to  11*5  and  9-99  per  square 
foot  of  grate.  The  coal  burned  per  square  foot  of  grate  area  was  25'94lb. 
against  22'52lb.  The  economy  of  consumption  was  in  favour  of  the  multi- 
tubular  boiler,  although  the  difference  is  not  great,  having  been  2'2561b. 


THE  MODERN  STEAM  BOILER. 


545 


per  I.H.P.  per  hour  against  2'24lb.  in  the  multitubular  boiler.  In  other  two 
trials  of  shorter  duration  the  water-tube  generator  only  required  2*216  and 
2'i87lb.  per  I.H.P.  hour  and  the  "Victory"  2'i81b.  The  water  evaporated  per 
Ib.  of  coal  was  7lb.  in  the  case  of  the  water-tube  boiler,  but  the  water  meter 
got  broken  in  the  "Victory."  The  "Victory"  steam  pressure  was  I75lb., 
and  the  funnel  5oft.  above  grate  gave  a  good  draught,  as  high  at  times  as  '4in. 
The  water-tube  boilers,  it  is  stated,  gave  no  trouble.  There  was  abundant 
steam  at  2Oolb.  pressure,  much  steam  being  wasted  through  the  blow-off 
valve,  owing  to  irregular  firing.  As  to  wetness  of  steam,  that  from  the  water- 
tube  boiler  was  always  drier  than  that  from  the  multitubular  boilers.  In  the 
former  case  the  amount  of  moisture  averaged  3-ioths  of  I  per  cent.,  against 
2f  per  cent,  in  the  case  of  the  Scotch  boiler.  Finally  the  weight  of  the 
water-tube  boilers,  including  fittings,  &c.,  under  steam  is  io61b.  per  I.H.P., 
less  than  half  that  in  the  case  of  the  multitubular  boilers  in  question. 


TABLE  XC. 

COMPARISON    OF    BOILERS    IN   STEAMERS 
AND  "VICTORY." 


ZENITH    CITY 


Kind  of  boilers  and  number      
Grate  surface        ...        ...        ...        ... 

2  Water-Tube 

I^d.  SO     ft 

2  Scotch 

Idd    SQ      ft 

Heating  surface 

6800  sq  ft 

"\7I^  SO    ft 

Ratio  of  heating  surface  to  grate 
surface 

co'7  to  I 

J/  *-J  °4-  •*• 

30/6  to  i 

Total  weight  with  water  ... 

Weight  per  square  foot  of  heating 
surface 

173,876  Ibs. 

2C-C7  Ihs 

335,787  Ibs. 

rS-7  ]hs 

I.H.P.  developed  

I  =540'  IO 

I4.l8'8 

I.H.P.  per  square  foot  grate  surface     ... 

Coal  burned  per  square  foot  grate 
surface 

11-15 

2X'Qd  Ibs 

r     9'99 

22-52  Ibs 

Coal  burned  per  I.H.P.  per  hour 

2-256 

24  hours 

2-24 
oi  hours 

Steam  pressure  per  square  inch 
Moisture  in  steam            
Weight  per  I.H.P  

200  Ibs. 
T^ths  of  i  o/0 
106  Ibs. 

175  Ibs. 
2f96 
213  Ibs. 

546 


THE  PRACTICAL  PHYSICS  OF 


TABLE  XCI. 

COMPARISON  OF  WARD  AND  COWLES  BOILERS. 


Ward.      ;    Cowles. 

Grate  surface                                                      s 

quare  feet 
quare  feet 

53            47 
2473-5    202675 
46-67        43-12 

Heating  surface                                                     s 

Ratio  of  heating  surface  to  grate  surface     ... 

Weight  of  boiler  empty,  no  smoke  pipe     ... 

tons 

11-84 

9-75 

Weight  of  boiler  with  water             

tons 

13*85 

"'55 

Boilers  for  "  Monterey  "         
Grate  surface  of  each  ... 

number 

4 
75 
2,938 

6 
47 
I998-5 

Heating  surface  of  each         

... 

Weight  empty  ... 
Weight  with  water 

tons 
tons 

I3-58 
15-86 
24 
70,022 

3,389 
66,633 

9-6 
12-65 

24^5 
45,620 

6,327 
39,293 

Duration  of  test 

hours 

Fuel  consumed,  total   ... 

pounds 
pounds 
pounds 

Refuse  from  fuel          ...        ... 

Combustible  consumed,  total  ... 

Total  feed  water          ...         
Temperature  of  feed   .. 

pounds 
degs. 
pounds 

461,885 

50-4 
1  60 

2 

280,822 
58 
1  60 

2 

Steam  pressure  ...         ... 

Air  pressure=inches  of  water          

Coal  per  hour  per  square  foot  of  grate  surface 

... 

55^5 

40-I9 

Combustible  per  hour  per  square  foot  of  grate  surface    ... 

52-4 

34-62 

Apparent  evaporation  from  feed  temperature 
temperature  per  Ib.  of  coal 

at  steam 

6'60 
6-93 

19,105 

7-724 
II39-5 

6-16 
7-15 

14-192 
7-002 
709-6 

Same  per  pound  of  combustible 

Actual  evaporation  per  hour  for  10  hours'  feed  at  120°, 
steam  160  Ibs.  pressure    ... 

Actual  evaporation  per  hour  per  square  foot 
surface 

of  heating 

H.P.  which  I  boiler  will  furnish  from  heating 
20  Ibs.  steam  per  I.  H.  P.  per  hour 

surface  at 

H.P.  from  whole  number  of  boilers 



4558 

4257-6 

THE  MODERN  STEAM  BOILER. 


547 


TABLE  XCII. 

COMPARISON    OF    RESULTS    OF    TESTS    OF    THE    WARD,   THE 

COWLES,    AND    THE    SCOTCH    BOILERS    OF    THE    "  SWATARA," 

EACH    MADE    WITH   AN  AIR   PRESSURE  =  2    INCHES  WATER. 


Ward. 

Cowle*. 

Scotch. 

i.  Coal  per  square  foot  heating  surface, 
per  hour 

Ibs. 
i'i795 

Ibs. 
•93204 

Ibs. 
1:0658 

2.  Combustible,     ,, 

1-1224 

•80278 

•8717 

3.  Water  evaporated,       „ 

6-8093 

57376 

6-9710 

4.  Equivalent   evaporation   from    and    at 
212°  and  atmospheric  pressure 

8-2941 

7-3287 

8-7678 

5.  Evaporation  per  hour  per  cubic  foot 
space  occupied,  and  as  above 

18:6075 

14-0188 

8-396 

6.  Evaporation  per  hour  per  ton  of  steam- 
ing weight,  and  as  above     ... 

I485-4 

1209-8 

455762 

T2 


548 


THE  PRACTICAL  PHYSICS  OF 


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11     Ilflli 


THE  MODERN  STEAM  BOILER. 


549 


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Wher««ed  

Outside  dimensions  

Grate  surface,  

Heating  surface  

Ratio  heating  surface  div.  by  grate  s 
Weight  of  boiler,  empty  
„  „  and  water, 
Duration  of  trial  —  

Air  pressure  in  inches  of  water  ... 

Feed  temperature  —  
Steam  pressure  above  atmosphere- 
Coal  per  hour  per  sq.  foot  grate  surfa 

Refuse—  
Moisture  
Superheating  

(a)  Apparent  evaporation  from  tern 
temperature  steam  per  Ib.  coal 

f  b)  Same  from  and  at  212°  Fah.  ... 

Actual  evaporation  as  in  (a) 

Same  as  in  fb)  

Actual  evaporation  from  and  at  212 
loot  of  heating  surface  

Horse  power  per  100  square  feet  of 
on  basis  of  18  Ibs.  steam  per  h 
112°  Fah  

Horse  power  per  ton  of  boiler  anc 
basis  

i 

« 

550 


THE  PRACTICAL  PHYSICS  OF 


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552 


THE  PRACTICAL  PHYSICS  OF 


Thornycroft  Boiler.  —  Careful  experiments  conducted  by 
Professor  A.  B.  W.  Kennedy  with  the  Thornycroft  Water-tube 
Boiler  gave  the  following  results  : — 

TABLE  XCV. 

TRIALS    OF    THORNYCROFT    MARINE    BOILERS. 


A 

D 

c 

B 

E 

Date          

Nov.  21,  1888 

Nov.  26,  1888 

Nov.  24,  1888 

NOV.  22,  1888 

Nov.  29,  1888 

Duration  

5  hrs.  2  min. 

4  hrs.  57  min. 

5  hrs.  9  min. 

4  hours. 

2  hours. 

Atmospheric  pressure  

14-80  Ibs.  per 

14-55  Ibs.  per 

14-80  Ibs.  per 

14-84  Ibs.  per 

14-45  Ibs.  per 

sq.  in. 

sq.  in. 

sq.  in. 

sq.  in. 

sq.  in. 

Boiler  pressure    

i86-oolbs.  per 

181-80  Ibs. 

171-20  Ibs. 

149-40  Ibs. 

180-50  Ibs. 

sq.  in. 

per  sq.  in. 

per  sq.  in. 

per  sq.  in. 

per  sq.  in. 

Boiler  pressure,  absolute 

200-80  Ibs. 

196.35  Ibs. 

186-00  Ibs. 

164-24  per 

I94"95  per 

per  sq.  in. 

per  sq.  in 

per  sq.  in. 

sq.  in. 

sq.  in. 

Air  pressure  in  stokehold 

O'OO 

O'OO 

0-27 

0-49  in. 

2'oo  in. 

Air  temperature  in  stokehold  ... 

— 

69-3°  Fah. 

71-4°  Fah. 

60-3°  Fah. 

62-1  Fah. 

Total  weight  of  coal  used 

1680-0  Ibs. 

1006-5  Ibs. 

2877-0  Ibs. 

3575-0  Ibs. 

3503-0  Ibs. 

Total  weight  of  ashes   

270-0  Ibs. 

233-5  Ibs. 

197-0  Ibs. 

— 

192-0  Ibs. 

Weight  of  ashes  re-used 

None. 

233-5  Ibs. 

1  70-0  Ibs. 

None. 

192-0  Ibs. 

Coal  burnt  per  hour     

334-0  Ibs. 

203-3  Ibs. 

559-0  Ibs. 

894-0  Ibs. 

1751-0  Ibs. 

Area  of  fire  grate          

30  sq.  ft. 

26-2  sq.  ft. 

30  sq.  ft. 

30  sq.  ft. 

26-2  sq.  ft. 

Coal  burnt  per  ft.  grate  per  hr. 

ii'iolbs. 

7-74  Ibs. 

18-60  Ibs. 

29-80  Ibs. 

66-80  Ibs. 

Total  feed  water  used  

— 

11291-7  Ibs. 

30141-0  Ibs. 

34332-0  Ibs. 

3  1  109-0  Ibs. 

Feed  used  per  hour       

— 

2281  Ibs. 

5852  Ibs. 

8583  Ibs. 

15554  Ibs. 

Feed  temperature         

78-4°  Fah. 

76-3  Fah. 

78-0  Fah. 

83-8°  Fah. 

ni-2°  Fah. 

Steam  temperature       

382°  Fah. 

380-2°  Fah. 

375-5°  Fah. 

365-5°  Fah. 

379-6°  Fah. 

Factor  of  evaporation  ... 

1-192 

1-194 

1-191 

1-182 

1-158 

Water  evap.  per  Ib.  fuel          \ 

(a)  Ash  not  re-used       ...       J 

— 

— 

— 

9-60  Ibs. 

— 

Water  evap.  per  Ib.  fuel          \ 

(b)  With  ash  utilised     ...       } 

— 

1  1'22  Ibs. 

10-48  Ibs. 

[io-2olbs.] 

8-89  Ibs. 

Equivalent  evaporation  from  ) 
and  at  212°  F.  (a)  \ 







1  1  -35  Ibs. 



Equivalent  evaporation  from  \ 
and  at  212°  F.         (b)          } 



13-40  Ibs. 

1  2-48  Ibs. 

[12-00  Ibs.] 

10-29  Ibs. 

Equivalent  evaporation  from  ") 

and  at  212°  F.  per  Ib.  car-  I 

bonjvalue  in  fuel    ) 

— 

13-08  Ibs. 

I2'i81bs. 

[i  1-70  Ibs.] 

10-04  Ibs. 

Temperature    of     gases     in  ) 

chimney       f 

474°  Fah. 

421°  Fah. 

540°  Fah. 

610°  Fah. 

777°  Fah. 

Air  pressure  in  chimney 

o'oo  in. 

o-oo  in. 

-f  0-03  in. 

+  0-12  in. 

+0-40  in. 

Total  heating  surface    

1837  sq.  ft. 

1837  sq.  ft. 

1837  sq.ft. 

1837  sq.  ft. 

1837  sq.  ft. 

Ratio  of  heating  surface    to  ) 

grate  area  j 

6l'2 

70-1 

61-2 

61-2 

70-1 

Water   evaporated    per    sq.  \ 

ft.  of  heating  surface  per  hr.  } 

— 

1-24  Ib. 

3-20  Ibs. 

470  Ibs. 

8-50  Ibs. 

Mean  rate  of  transmission  of  ) 

23-8  heat 

6ro  heat 

89  heat 

158  heat 

heat  per  sq.  ft.  H.S.  per  min.  / 

— 

units. 

units. 

units. 

units. 

Lbs.  coal  per  I.H.P.  per  hour  ... 

2-220 

2-280 

1-981 

i-ooo 

2-260 

Efficiency  of  boiler       

— 

86-8  per  cent. 

81-4  per  cent. 

78-2  percent. 

66-6  per  cent. 

Descriptive  details  of  these  trials,  with  analyses  of  the  fuel 
and  gases,  and  statements  of  the  heat  balances,  will  be  found  in 
Professor  Kennedy's  Report,  which  is  attached  to  Mr.  Thorny- 
croft's  paper  in  Min.  Proc.  Inst,  C.  E.,  Vol.  xcix.,  pp.  41-147. 


THE  MODERN  STEAM  BOILER. 


553 


Belleville  Boiler. — The  following  results  afford  a  contrast  in 
some  points  between  the  ordinary  cylindrical  or  "  Scotch " 
boiler  and  water-tube  boilers  of  the  Belleville  design.  The 
experiments  were  published  under  the  authority  of  Mr.  Samson,  of 
Messrs.  Maudslays,  the  British  makers  of  the  Belleville  boiler : — 

In  order  to  ascertain  the  comparative  evaporative  efficiency  between  the 
ordinary  cylindrical  single-ended  boiler  and  boilers  of  the  Belleville  type,  the 
following  trials  were  made  : 

A  vessel  with  cylindrical  single-ended,  three-furnace  boilers  was  selected. 
Two  of  these  boilers  worked  in  battery  were  used,  the  total  grate  surface 
being  138  square  feet,  and  the  total  heating  surface  3,880  square  feet.  A  group 
of  four  Belleville  boilers,  having  a  total  grate  surface  of  135  square  feet,  and 
heating  surface  3,842  square  feet,  was  then  selected  for  experiment.  It  will 
be  observed  that  as  regards  grate  and  heating  surface,  the  boilers  above 
mentioned  are  practically  identical,  the  cylindrical  with  the  water-tube.  Trials 
were  made  in  order  to  ascertain  how  many  pounds  of  water  could  be  converted 
into  dry  steam  per  pound  of  coal,  burning  the  same  with  natural  draught  and  at 
approximately  equal  rates  of  combustion.  The  vessels  were  moored  along- 
side the  quay,  and  the  water  was  taken  from  the  town  main  and  measured 
carefully  into  tanks  before  being  pumped  into  the  boilers.  The  trials  were 
made  at  the  same  place,  by  the  same  staff,  with  the  same  quality  coal,  and 
under  as  nearly  as  possible  the  same  conditions,  in  order  to  render  the 
comparative  trials  perfectly  fair.  The  results  were  as  under  : 


BELLEVILLE 
Four  Boilers — 

Total  heating  surface 
„     grate 


TABLE  XCVI. 

BOILERS  -EVAPORATIVE  TRIALS. 


3842  sq.  ft. 
135      „ 


Water 

Coal  Con- 

Evapo- 

Duration 
of  Trial. 

;     sumed  in 
Pounds 
per  Square 
Foot  of 
Grate. 

rated  per 
Pound  of 
Coal  from 
Tempera- 
ture of 

Equivalent 
Evapora- 
tion from 
and  at 

212°. 

Steam 
Pressure 
in  Boilers. 

Tempera- 
ture of 
Feed 
Water. 

Quality  of 

Feed. 

hours 

lb. 

lb. 

deg.  Fahr. 

8 

18-8 

8-3 

10-24 

200 

40 

Best 

8 

I9'43 

9-1 

H'22 

200 

40 

Welsh 

.  i 

8 

19-4 

9-0 

H'09 

2OO 

40 

M 

8 

24-5 

7-83 

9-58 

200 

50 

>» 

8 

I2'0 

8-5 

10-38 

200 

So 

)) 

8 

I2'0 

9-16 

ir30 

200 

50 

n 

8 

9'2 

8-64 

10-57 

2OO 

50 

)i 

554 


THE  PRACTICAL.  PHYSICS  OF 

TABLE  XCVI.  continued. 
SINGLE-ENDED    CYLINDRICAL   BOILERS. 


Grate  surface 
Heating    „ 


138  sq.  ft. 
3880     „ 


Water 

Duration 
of  Trial. 

Coal  Con- 
sumed in 
Pounds 
per  Square 
Foot  of 
Grate. 

Evapo- 
rated per 
Pound  of 
Coal  from 
Tempera- 
ture of 

Equivalent 
Evapora- 
tion from 
and  at 

212.° 

Steam 
Pressure 
in  Boilers. 

Tempera- 
ture of 
Feed 

Water. 

Quality  of 

Feed. 

hours 

Ib. 

Ib. 

deg.  Fahr. 

8 

12 

7'59 

I24 

50 

Best 

8 

2O 

8-02 

I24 

50 

Welsh. 

8 

28 

7-85 

I38 

50 

M 

8 

12 

8-44 

110 

50 

„ 

8 

20 

8-09 

110 

50 

H 

8 

28 

7-86 

132 

50 

» 

It  should  be  noted  that  Hie  above  results  were  obtained  from  cold  feed  water, 
and  that  the  water-tube  boiler  raised  steam  to  200  Ib  pressure  against  the 
cylindrical  boiler  at  from  no  Ib.  to  138  Ib. 

This  was  necessary  in  order  to  make  the  comparative  trials  perfectly  fair, 
because  although  in  the  Belleville  boiler  steam  was  raised  to  200  Ib.  per 
square  inch,  it  was  reduced  to  135  Ib.  per  square  inch  at  the  engines,  whereas 
in  the  cylindrical  single-ended  boilers  the  engines  were  supplied  direct  from 
the  boiler  at  the  working  pressure. 

The  cylindrical  boilers  were  to  Admiralty  scantlings,  and  weighed,  together 
with  water,  lagging,  fittings,  and  uptakes  complete,  about  100  tons.  The 
Belleville  boilers  weighed  with  castings,  brickwork,  fittings,  water,  and  all 
appurtenances  peculiar  to  the  system,  about  50  tons,  showing  a  saving  of,  say, 
50  tons  in  favour  of  the  water-tube  boiler. 

Some  interesting  results  obtained  from  trials  with  Lagrafel- 
D'Allest,  Niclausse  and  other  boilers,  and  arranged  for  comparison 
with  some  cylindrical  boiler  tests,  were  given  by  Mr.  J.  T.  Milton, 
Chief  Engineer-Surveyor  of  Lloyds  Register,  in  a  lecture  on 
water-tube  boilers  at  the  Royal  United  Service  Institution 
(June  26th,  1895).  They  were  as  follows  : — 


THE  MODERN  STEAM  BOILER. 


555 


556 


THE  PRACTICAL  PHYSICS  OF 


to, 

£  rt  rti 

^2  c    - 

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b       b       M 


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inical  Engineers. 

Scotch  Coal  of  12,71 
rific  value. 

West  Hartley  Coal 
Calorific  value. 

Yorkshire  and  Notti 
13,280  T.U.  Calor 

Northumberland  i 
T.U.  Calorific  val 

Patent  Fuel,  14,39 
rific  value. 

oJ 

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THE  MODERN  STEAM  BOILER.  557 

The  following  results  were  published  by  Sir  John  Durston  * : — 

TABLE  XCVIII. 


Equivalent  evapo- 

"5 . 

"t*  *o 

ration  from  and 

"« 

ssf  «! 

at  212  deg.  F. 

12 

Name  of  Ship  and  Type  of 

3  3 

-  j  2 

J^ 

Boiler. 

3H 

O  u  W 

Per  sq.  ft 

•st 

Remarks. 

Q 

^   fi« 

heating 

Per  Ib. 

ol 

surface 

of  coal. 

^"C 

Ibs.  per 

p.  hour. 

x  2 

Hours. 

hour. 

"  Seagull."  fitted  with  Niclausse  ) 

8 

14-60 

4-91 

1077 

3i'9 

Trials  on  board. 

boilers    / 

8 

24-20 

7-3I 

9-61 

31-9 

Trials  on  board. 

"Sheldrake,"  fitted  with   Bab-) 
cock  and  Wilcox  boilers      ...  f 

5 
8 
8 

22-50 
15x0 
25-00 

5'95 
5'29 
7-68 

I2'IO 

12-70 

II'IO 

457 
36-1 
36-1 

Trials  on  shore. 
Trials  on  board. 
Trials  on  board. 

"Sharpshooter,"     fitted     with  t 
Belleville      boilers     without  < 
economisers     ( 

8 
8 
8 

21-00 
13-IO 
9-90 

7-85 
470 
3'53 

1  1  '05 
10-65 
10-55 

29-6 
29-6 
29-6 

Trials  on  board. 
Trials  on  board. 
Trials  on  board. 

Belleville    boiler    with    econo-  f 

misers.     Average  of  several  < 

4 

30-I3 

"79 

11-67 

31-3 

Trials  on  shore. 

trials      [ 

Particulars  of  extended  trials  of  some  of  these  boilers  are 
given  in  the  following  Table,  which  was  first  published  in  the 
Naval  and  Military  Record  of  November  23rd,  1899.  That  paper 
remarked  that  : — 

At  present  the  gunboat  Seagull  which  has  been  fitted  with  the  Niclausse 
type  of  water-tube  boiler,  is  being  subjected  to  exactly  similar  experimental 
tests  as  the  Sheldrake  and  Sharpshooter  have  undergone,  the  former  recently 
with  the  Babcock  and  Wilcox  type  of  water-tube  boiler,  and  the  Sharpshooter 
a  few  years  since  with  the  Belleville  class.  When  the  Seagull  has  completed 
her  programme,  the  results  of  the  working  of  the  three  types  of  boilers 
will  be  collated  for  purposes  of  comparison  as  to  their  respective  merits. 
As  this  comparison  is  likely  to  be  made  early  in  the  ensuing  year,  it  may 
be  interesting  to  give  the  hitherto  unpublished  return  relating  to  the  trials 
of  the  Sharpshooter  and  Sheldrake. 


See  Min.  Proc.  Inst.  C.E.,  Vol.  cxxxvii.,  p.  213. 


THE  PRACTICAL  PHYSICS  OF 


o 

2 

g 

T»" 

a  a 


j  M 


Q 


v,    v,    o"'    S' 

b    o    bv  'os    :::::::::::: 
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III  III 

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2  ^    :  -g  -g      -g      -8 

Hirl         I   If    . 

.u   .H   .5    «? 


•.•Yiflfl1 

ft  8  I  5 

-' 


*       »      3     •! 


B   2   E 


THE  MODERN  STEAM  BOILER- 


559 


w 


8 


L 


8 s  o  s  s  s 


f?  P 

30      O 


ooo     :£?oooooooooo 


§  J  3  J»  S  |  J 


-  «-  «•  tf  « 


I  i  1  •.••••!  - 

.8    J    §      =     s     s     t    S      ; 


!  i 


THE  PRACTICAL  PHYSICS  OF 


rt 

!<8i&* 
S  Q    M    o    5?  S 

^Q     ^  ^  « 


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1  «•  2 

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'  5         i  1    ?        II 


THE  MODERN  STEAM  BOILER.  561 

The  preceding  Table  is  from  a  paper  "  On  the  Boiler  arrange- 
ments of  certain  recent  cruisers "  by  Mr.  F.  T.  Marshall, 
M.I.N.A.  The  vessels  referred  to  are  H.M.S.  "Andromeda," 
built  at  H.M.  Dockyard  at  Pembroke  ;  H.R.  Portuguese 
M.S.  "Don  Carlos  I.",  built  at  Elswick  ;  H.I.  Chinese  M.S. 
"  Hai  Tien "  and  "  Hai  Chi,"  sister  vessels,  also  built  at 
Elswick  ;  and  H.M.S.  "  Hermes,"  "  (Eolus,"  and  "  Pallas,"  the 
two  latter  being  included  as  being  typical  second  and  third 
class  cruisers  with  cylindrical  boilers. 

Boilers  in  the  British  Navy. — A  comprehensive  view  of  the 
position  as  regards  boilers  in  the  vessels  of  the  British  Navy  is 
afforded  by  the  Tables  given  in  Sir  John  Durston's  two 
papers  on  "  The  Machinery  of  Warships." 

The  fallowing  Table  is  taken  from  the  latter  paper  on  account 
of  the  details  of  dimensions  which  it  gives. 


TABLE  CII. 


S5 

IRT 

^ 

W.ifbt  *f  MMLlMry  tMklD)  tuladlaf  AaxltluiM  «a4 

II 

£7&».Ui.u 

fed-fecm. 

(.lUrRwiu. 

«r 

ss 

P«  IBP 

»^4 

Unfa. 

«M. 

ll! 

Br 

mjt; 

TlfcT 

F-i.    F- 

r«.     r«t 

T«. 

i^i 

LU. 

jj-g. 

,^.. 

|-«  Mk,.u 

MtJMtio  ' 

155 

a)  11.000 
6)  10,000 

43  5x48  0 

(l)OMO 

n-ixit-s 

(»)  0-862 

(t)0-562 

443 

71! 

M 

161 

(I)  159 

(50 

II 

109 

0 

e)    6.000 

i«j|'<a)    9  COO 

Trau 

it.1  W    '•00° 

48  0x33  5 

(t)0  SOO 

(1  OxM-O' 

WO-  MS 

1)0  583 

171 

547 

78 

158 

(.6)  291 

910 

M 

140 

Iau|.(e)    4,800 

A 

Koj.l 
Smrcfgn' 

155 
tM 

ud  11.000 
(I)    9,000 

44  0x400 

(»)0  1% 

760x400 

(1)0-540 

W05M 

807 

393 

M 

148 

i»j»« 

918 

11 

100 

(«)    5,400 

(a)  12,000 

:rcKtnt 

<6)  10,000 

|40-0x46-0 

(1)0184 

93-3x37-0 

(t)  0-845 

(t)0-530 

MS 

614 

12 

144 

(6)2)4 

850 

M 

100 

M     6,000 

60-0x42-0 

(»)  0-103 

Pow,rfuP 

Mi 

210 

(6)  23^000 
(«)  18.000 

8  0x28-0 
for 

0-02- 

(MJ-Ox42-fl\ 
74-0x34  OJ 

(*)0290 

(»)0  418 

7*> 

1154 

M 

IM 

»» 

MO 

M 

110 

Am*«>t 

M 
MCI 

;»)  10^000 

48-0x35  5 

(»)  0-171 

101-0x81-0 

(1)0  313 

4)0  484 

188 

i«S 

« 

- 

., 

... 

33 

140 

ft*. 

300 
Ml 

(a)    7.000 
(f>)     5,000 
(e)    8,500 

37  8x34-0 

«.» 

(0-0x24-0 

»)0  384 

m^. 

M 

ITS 

« 

» 

141 

« 

r 

no 

1- 

'£ 

Si  10' 

M»; 

8| 

=| 

(«)      .. 
'4)  16.500 
(0  12,400 

(a) 
(6)  18.000 
(«)  1*500 

i«)  10.250J 

55-3x43  i 
55-0x43-0 
M  0x48-0 

('00-147 
WO-IM 

6«-Ox36-0| 
6«  0x40-0) 

/  66  0x39  Oi 
U-OX34-5/ 

84  0x43  25 

(6)0-805 

... 

(,)•  iii 

1)0-100 

(DO-4M 

(91 

440* 

7« 

791 
6M- 

74 

73- 

104 
M 
104.' 

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m« 

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ii« 

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562- 


THE  PRACTICAL  PHYSICS  OF 


In  his  paper  on  "  The  Machinery  of  Warships/'  in  1894^ 
Mr.  Durston  gave  details  of  the  machinery  fitted  in  the  70 
vessels  built  under  the  Naval  Defence  Act  of  1889.  In  "  Recent 
Trials  of  the  Machinery  of  Warships,"  published  in  1899,* 
Sir  A.  J.  Durston  and  Mr.  H.  J.  Oram  give  similar  details 
of  the  vessels  added  to  the  Royal  Navy  since  the  former  date. 

It  appears  that  ten  Battleships  with  water  tank  boilers, 
which  are  among  the  recent  additions  to  the  Navy,  have  a 
larger  proportion  of  heating  surface  than  former  examples,  in 
consequence  of  the  recommendation  contained  in  the  1893 
Report  of  the  Admiralty  Committee  on  the  designs  of  machinery 
for  warships.  The  results  as  to  weight  of  machinery  are  briefly 
as  follows  : — 

EIGHT  VESSELS  BUILT  UNDER  NAVAL  DEFENCE  ACT. 


Mean   I.H.P. 
developed. 

Average  Steam 
Pressure- 
Boilers. 

Heating  Surface 
per 
I.H.P.  (mean). 

Weight  in  Ibs.  per  I.H.P. 

Engines. 

Boilers. 

II500 
9430 

149 
ISO 

17 
2'I 

113 
146 

1  16 
141 

AVERAGE  OF  TEN  BATTLESHIPS  BUILT  SINCE  1893. 


12414 

149 

2'0 

III 

131 

10404 

148 

2'4 

132 

156 

6170 

140 

4'  I 

261 

486 

Eight  of  these  vessels  are  fitted  with  forced  draught  on 
the  closed  stokehold  system,  and  two  of  them  with  induced 
draught  apparatus,  similar  to  what  was  originally  tried  in 
the  "  Gossamer,"  artificial  draught  being  used  in  all  of  them  for 
obtaining  maximum  power. 

The  I.H.P.  developed  per  ton  of  machinery  is  less  than  in  the 
eight  vessels  compared  with  them,  but  the  engines  were 
made  rather  more  substantial,  and  the  additional  size  of  boilers 
is,  of  course,  also  responsible  for  increased  weight. 


1  Min.  Proc.  Inst.,  C.E.,  cxix.,  pp.  17— 46. 

3  Min.  Proc.  Inst.,  C.E.,  cxxxvii.,  pp.  202—241. 


THE  MODERN  STEAM  BOILER. 


563 


Ten  first  class  Cruisers  with  triple-expansion  engines,  having 
four  cylinders  and  four  cranks  and  with  Belleville  boilers, 
give  better  results.  The  "Powerful"  and  "  Terrible"  with 
48  boilers,  without  economisers,  give  : — 


I.H.P.  developed. 

Steam  Pressure  — 
Boiler. 

Heating  Surface 
per  I.H.P. 

Weights  per  I.H.P. 

Engines. 

Boilers. 

5058 

2I6-5 

— 

— 

— 

18479 

227-5 

3-66 

130 

140 

22547 

23I-0 

3-00 

TO/ 

H5 

25774 

243-0 

2-63 

94 

100 

The  I.H.P.  per  ton  of  machinery  for  the  three  higher 
powers  is  8^29,  lo'io,  and  11*55.  ^n  the  "Ariadne,"  fitted 
with  30  Belleville  boilers  with  economisers,  it  is  12-14  f°r 
19,156  I.H.P.,  with  2-47  square  feet  of  heating  surface  per 
I.H.P.,  and  a  weight  of  91  Ibs.  per  I.H.P.  for  the  boilers  and  93 
for  engines,  the  steam  pressure  at  boilers  having  been  288  Ibs. 
per  square  inch. 

In  the  second  class  Cruisers  fitted  with  cylindrical  boilers 
we  have  : — 


I.H.P.  developed 
(mean). 

Steam  pres- 
sure —  Boiler. 

Heating  sur- 
face per  I.H.P. 

Weights  per  I.H.P. 

Engines. 

Boilers. 

Forced  draught 

98467 

I5ro 

1-88 

84 

124 

Natural  

8307-8 

I50-0 

2-23 

99 

I48 

I.H.P.  per  ton  of  machinery  at  higher  power  9-07  :  whilst  for 
vessels  of  the  same  class,  fitted  with  18  Belleville  boilers  of  eight 
elements  without  economisers,  we  have  : — 


I.H.P. 
developed. 

Steam  pressure  — 
Boiler. 

Heating  surface 
per  I.H.P. 

Weights  per  I.H.P. 

Engines. 

Boilers. 

10240 

265 

2-49 

82                      99 

. 

5^4 


THE  PRACTICAL  PHYSICS  OF 


Third  class  Cruisers  and  Torpedo-boat  Destroyers  show 
similar  results,  Sir  A.  J.  Durston  having  said  that  no  difficulty 
had  been  experienced  in  working  with  a  boiler  pressure  of 
300  Ibs.,  and  an  engine  pressure  of  250  Ibs.,  and  that  the 
influence  of  increased  pressure  of  steam  on  the  economy  of 
weight  and  space  had  been  considerable. 

Mail  Steamers. — In  Mail  Steamer  work,  according  to  Mr. 
List,  the  limit  of  steam  pressure  with  tank  boilers  has  practically 
been  reached.  They  are  using  double-ended  8-furnace  boilers, 
17  ft.  mean  diameter,  and  19  ft.  2  ins.  long  for  a  working 
pressure  of  210  Ibs.  per  square  inch.  The  boiler  shell  plates  are 
i£J  inch  thick,  and  the  furnaces  are  44  inches  internal  diameter 
and  -JJ  inch  thick  ;  the  steel  of  the  shells  having  an  ultimate 
tensile  strength  of  between  31  and  34  tons  per  square  inch.  The 
weight  of  such  a  boiler,  with  mountings,  is  115  tons,  with 


TABLE 


a  is 

m 

m 

as 


!l 

1 


.  .  >. 

Hone-pawn  denloped  on  tri.t  .         . 

Gjal  bant  per  «q  ft.  of  grate  . 

Ooml  burnt  per  bom-power  per  bow  on  trial  . 


.  par  M|.  l». 
O    iq.  ft 

VI 


Stop,  Kf.tr.  blow-off,  aod  ndaciBg  T,|T«,  Mpumton 

•&3.X 

Total  mich*.  1 


FWd-p»»» 

read-wale*  Unit  ud 
Peed-water  bailor. 


48,926 
430.C46 
S71  1 


MM 

48.S02 

MM 


191.701 
14,870 
31.118 


ttRSBS  TO01iUD   •o"™ 


18.526 
8,168 
21-21 
I-80K 


311,97} 
492  7 


12.  7« 
37,479 
15.185 


147-1 
493 

4»,036 
99.539 
48,990 
129,278 
13,669 
19^2 

345,354 

497  6 


737  6 
21, 3» 
9,440 
25  6N 


J1.1C5 
12.588 


25,333 


123,412 
162  » 


33,713 
107,951 

61,377 
147.981 

13,143 

27.970 

396,137 


32,175 
13,817* 
27  3<i' 
2235' 

346,357 
l!4,7«4 

76,059 


476  ? 
1-97 

29,489 
12,123 

IfJM 
16.534 
63,934 
40.345 


158-9 
5-81 

65,257 
163.018 

95.9<r2 
192,117 

24.251 

42,990 

383,533 
317-1 

.299,1197 
.180-38 

1152  4 
12-23 


2.196 
1,000 
37-07 
1-331 

17,637 
7,71« 

2',  205 
27.358 
438  S 


75  2 
2-03 


1,190 

IsioeT 

2877 


1.074 
19,.122 


3.404 
189 


9,735 
201  2 


409,904 
37.700 
37,762 

751-4 
»•& 

W.360 
7.302 


76,896 

11,153 


12:4.735 

I9l-t 

6-S7 

110.241 
K9.3M 

37.9m 

17,637 
18,409 
19.396 

292,978 
4535 


THE  MODERN  STEAM  BOILER. 


565 


49 J  tons  additional  for  water.  In  a  comparative  estimate 
of  Belleville  boilers  suitable  for  the  same  work,  but  at  300  Ibs. 
pressure,  it  appeared  that  they  would  have  4^  per  cent,  less 
total  heating  surface  than  the  tank  boilers  ;  they  would  weigh 
40  per  cent,  less,  and  save  in  length  of  space  13  per  cent., 
but  would  cost  50  per  cent,  more  in  first  cost. 

Boilets  in  French  Navy. — In  the  French  Navy  several  vessels 
have  been  fitted  with  water-tube  boilers,  the  designs  chosen 
being  those  of  the  Belleville,  0 nolle,  D'Allest,  Niclausse,  Du 
Temple,  Du  Temple-Guyot,  Nonnand,  Nonnand-Sigaudy,  and 
Thorny  croft  boilers.  A  comparative  view  of  these  is  given 
in  Table  CIII.,  taken  from  M.  Bertin's  work  on  "  Marine 
Boilers,"1  from  which  much  interesting  information  may  be 
obtained  on  this  subject : 
1  English  Translation  by  Mr.  L.  S.  Robinson  (London.  John  Murray,  1898). 


CIII. 


E 

r-Al-LMT 

NICLAVWr 

1 

1C   TXHr 

IB 

KOB1 

IAMD 

81(3  AUDI 

DU  TEMPLE 
OUTOT. 

THORNY 

CBOIT. 

••tSSir 

C*-,,, 

CAUIOT 

OUYLL 

r*u«T 

01  A  00  S. 

•ffissa1- 

aHA 

.3E& 

SS?^. 

1*..    !»*.   IM 

]«:«. 

SB3t?: 

numu-vac 

TIUJCl 

is 

IU 

119 

tit 

8 

1M 

IW 

IM 

IW 

•in 

iiaf 

IW 

It.iM 

1»,M7 

17,101 

W,S» 

».S40 

t.W7 

I.1M 

1,899 

«4:m 

Tfl.fTS 

4.  It* 

t.sn 

l.»l 

M.MS* 

l.S76» 

t,4as 

I.MS 

l,l«l 

*',»! 

1,17* 

I.SB9 

M.760 

M.IM 

MM 

•1-27 

SO  71 

•0  71 

14  U 

W74 

•1  M 

«4I 

•7-8S 

M  II 

w:7 

M:t 

*t  44 

1-77* 

I'M* 

J  OS 

t-MI 

1  OM 

1  IJ» 

i  «n 

i  «n 

1  W 

I'M 

1  DOT 

§03.751 
«*.«77 

171,664 
M.Sl* 

no,  >n 

M.iM 

Wt.470 

n.oM 

4M.OM 

m 

M.M) 

M.I7I 

»,m 

I7,»l» 

lft.4«7 

W0.97U 
44.002 

171.  MO 
4I.SOI 

•1.74* 

l.»m 

41,  OM 

I7,ll» 

W.008 

74,964 

41.104 

«.0» 

1.04S 

1.771 

(M 

M*» 

III.MO 

130.940 

J./7« 

178.  »7 

2(4,801 

141.  M* 

M.47U 

447.«tl 

w.nc 

t».61S 

t7.VI» 

is.aos 

M.4M 

7*8.  Wl 

i.  on  .isi 

M.on 

»i7-i 

614 

W  » 

MI  1 

<7I  7 

4M« 

K7  « 

Mt  • 

SMI 

Ml* 

SU-H 

Mt  1 

474-1 

141 

t  M 

til 

1  M 

1  « 

in 

IW 

1  M' 

If* 

t  W 

2  (1 

«  M 

IM 

11,«M 

»,M4 

13.7V3 

t.4M 

14.14* 

M 

7U 

•71 

ir> 

S0» 

*7,S» 

Ib.MS 

fwsi 

I.WI 

4,101 

11.228 

t.tf* 

I1.9SH 

*44 

I.4S7 

M 

4S6 

MO 

S,*S4 

ll.ttt 

s» 

J.805 

I.MO 

l.tTB 

I.C40 

UM 

1.071 

!S04 

«.*07 

SOI 

4,OM 

S.M6 

1.97(1 

4«7 

17,837 

ft.Ui 

441 

S3 

M 

IlilM 

I.4M 

».l>4 

MA 

l» 

Ml 

IS3 

iia 

M.OI4 

fl.MS 

069 

4«.»7 

M.OW 

49  170 

4.41D 

4.141 

l.0» 

1.7*4 

1.174 

101.410 

ISO.  1/70 

1.197 

10.7* 

Stl 

14,  Wl 

10.141 

10.  MO 

4IS 

m 

m 

sn 

m 

M.IM 

M.ftil 

•M 

KS.DI7 
IS  » 

«« 
*4 

lll.M* 
110  t 

71.  *U 
100  1 

1  01.871 

isa-7 

7.7M 

MM 

».77l 

m-» 

S.77S 
101  « 

4.117 
111  1 

4.SI1 
III  4 

AM,  MO 
117   11 

MO.IU 
IM  1 

4f«3S 
Ml 

1  M 

••4 

t  t 

1  27 

»  u 

I'M 

«• 

1  t 

1  74 

1  «4 

6  W 

4  n 

1  OS 

1  19.  01* 

9fl« 

lll.<*l 

116  8.SO 

IAI.4IS 

4.1M 

s.»«« 

V.4SS 

8    '11 

S.M1 

194.000 

191.410 

I.4UC 

76.223 

i"7J 

160.9S7 

ll«,««0 

72,  7M 

4,  Ml 

S.MI 

S.MU 

V.UI 

l.VM 

rw.ivo 

I»I.S!0 

*.I!O 

I4S.6GU 

,991 

IS3.IJ9 

8t.«n 

»I.Mt 

i.  in 

1,«M 

1.101 

171 

970 

2OV.440 

IS).  000 

i.  ata 

7.IM 

53S 

U.OM 

It.  431 

1,907 

M» 

1.9S4 

MO 

Vi4 

3I.9C7 

17,471 

»|0 

I6.SS2 

,W2 

S4.»l 

li.«31 

16.SU 

441 

MS 

wn 

••17 

M 

4i,T09 

44.0M 

*.  Sin 

M.7II 

,•93 

S9.U83 

M,H4 

It.M* 

1.101 

8flO 

I.IM 

«M 

61.70 

47.3WI 

M 

M4.4M 

180,792 

461,737 

179,  tM 

>«l.»4> 

IS.  701 

l«.i*J 

V.IS4 

II.U41 

II.1SI 

74M.OM 

7lM.«M 

l».»l« 

W»  » 

4*8.1 

«t  1 

MIS 

133  f 

14*  1 

Of  4 

III  7 

MM  1 

no  I 

Ml  W 

430  4 

MS 

ITS  2* 
lltt 

.njj. 

Jtti-t 

Ml   44 
Ittl-l 

»7»  W 
11*9  « 

361   It 

ita» 

17  M 

7i3  4 

U  1 

•714  • 

*  u 
Ml  * 

IS  II 
•41  4 

u  ou 

•31 

7*9  4 
I.OM  W 

(04  » 

1.0!   4 

17  14 
7M  • 

»•• 

74'» 

»> 

10  ) 

HI 

•  1 

U  » 

»  4 

n 

as 

71  » 

7<  W 

A 

566 


THE  PRACTICAL  PHYSICS  OF 


D' Attest  Boiler.— Trials  with  the  D'Allest  boilers  gave  the  fol- 
lowing results  : — 

TABLE  CIV. 


Vessels. 

Bombe. 

Cassini. 

Chasseloup- 
Laubat. 

Jemmapes. 

COAL  CONSUMPTION  TRIALS. 

Boiler  pressure,  Ibs.  per  sq.  in. 

I25-0 

I63-5 

I7ID 

I59-3 

Pressure  at  reducing  valve 

114-61 

i5i'05 

I35-58 

166-98 

D2 

Expansions  A  =  —  -  ... 
i  a* 

4'39 

8-6 

12-59 

11-86 

Lbs.  coal  consumed  :— 

Per  sq.  ft.  of  grate 

21-074 

20-115 

10-85 

I47I5 

Per  H.P.  hour       ... 

2-092 

1-817 

1-48 

2'0 

SPEED  TRIALS. 

Boiler  pressure,  Ibs.  per  sq.  in. 

13974 

I95-57 

184-9 

203-82 

Pressure  at  reducing  valve     ... 

II9-474 

I7r95 

159-88 

184-88 

D2 

Expansions  A  =  —   

378 

6-84 

7*34 

8-763 

Lbs.  coal  consumed  :  — 

Per  sq.  ft.  of  grate 

48-25 

31-273 

23-88 

30-122 

Per  H.P.  hour       

2-374 

1-947 

1-779 

2'IOI 

THE  MODERN  STEAM  BOILER.  567 

yiclausse  Boiler. — Trials  with  the  Niclausse  boiler  on  board 
the  warship,  "  Friant,"  with  careful  and  regular  stoking  gave 
the  following  results  : — 

COAL     CONSUMPTION     TRIALS. 

Boiler  presure,  Ibs.  per  sq.  inch        ...         180 

Pressure  at  reducing  valves,  Ibs,  per  sq.  inch         ...      141-6 

D2 

Number  of  expansions  in  engines,  A  =  ^—5  ...       12.40 

Coal  burned  per  sq.  ft.  of  grate,  Ibs.  10*25 

Coal  burned  per  H. P.  hour ...        1-49 

SPEED   TRIALS. 

Boiler  pressure,  Ibs.  per  sq.  inch     J94'57 

Pressure  at  reducing  valves,  Ibs.  per  sq.  inch        ...     163*14 

D  2 
Number  of  expansions      =^-TJ •••     7'^3 

Coal  burned  per  sq.  ft.  of  grate,  Ibs ...  25-03 

Coal  burned  per  H.P.  hour      ...         ...  2*032 

It  is  stated,  by  M.  Bertin,  that  a  boiler  in  the  works  of 
M.  Niclausse,  under  forced  firing  has  shewn  a  rate  of  evapora- 
tion equal  to  72  Ibs.  of  water  per  square  foot  of  heating  surface, 
without  injury  to  the  tubes,  although  the  chimney  was  burnt 
through.  These  experiments  were  designed  to  prove  the 
indestructibility  of  the  boiler,  apart  from  any  expectation  of 
obtaining  economy  of  steam  generation. 

In  trials  of  the  Niclausse  boilers  of  the  torpedo-boat 
"  Temeraire,"  on  shore  in  1897,  rates  of  evaporation  of  11*25, 
10*12,  10-72,  and  io'3  Ibs.  of  water  from  and  at  212°  Fah.  per  Ib. 
of  coal  were  obtained  with  draught  pressures  of  i'i,  1*5.  2-7  and 
4-3  inches  of  water  respectively,  the  rates  of  combustion  having 
been  41,  51*2,  66-5  and  81-7  Ibs.  of  coal  per  square  foot  of  grate. 
The  evaporation  in  Ibs.  of  steam  per  square  foot  of  heating 
surface  is  stated  as  having  been  for  these  rates  of  combustion 
4.6,  io'6,  13*2,  and  15-9  Ibs. 

The  following  figure  shows  these  results  plotted  in  curves. 


568 


THE  PRACTICAL  PHYSICS  OP 


Date  September.  1896. 
Duration  of  trial 


hours 


Ibs.   of  water  evaporated    per   tb.    of    \^*-f 
coal  from  and  at  212* 


Ibs    of  water  evaporated    per    Ib.    of 
coal  under  actual  conditions 


Steam   pressure   tn    Boiler,   above  at- 
mosphere 


Ibs.  of  steam   evaporated  per  sq    ft.    , 
of  Heating  Surface 


Draught  at  base  of  Funnel,  In  Inches 
of  water 


Feed  temperature,  Fahn 


Ibs.  of  Coal  burnt  per  «q   ft.  of  grate     44  5<  t 

FIG.  312. 


66s 


Further  results  with  Niclausse  boilers  are  given  by  Mr.  Mark 
Robinson  in  Trans.  Inst.  N.A.,  Vol.  37,  pp.  119 — 134,  and  by  M. 
E.  Duchesne  in  ."  Quelques  Resultats  d'essais  de  Chaudieres 
Militaires  Marines  "  (Mem.  et  Compt.  Rendu  de  la  Soc.  des 
Ingenieures  Civils,  January,  1898,  pp.  54 — 69). 

From  the  former  the  following  results  are  taken  : — 


THE  MODERN  STEAM  BOILER. 


569 


W     C/3 

P 


w 

1" 


si  «° 

<     a 

H  M       C_| 


w 


Ed 


ill  fn 

•s    1   | 

x? 

|  S  g  1  f 

hi: 

£       <8         $       £       ? 

O\      o\      F*     do      do 

!Hs 

b    5>    *    «t    a 

fl        00          «O        UO         O\ 
O         t^        'J'       u^        O 
•*•       N        VO         10       «0 

lit3 

0?        VO          K         Ov        00 

j>{> 

1  1  s  &  s 

|   S. 

«  1  1-  1  f 

1  ?  1 

H 

&      3-      °      y>      .•*• 

c 

S    2     ;?    S    b 
"2     £r    «•    «     Er 

§     » 

H 

00         30           Tf-        00         00 

Date  of  Trial,  1895. 

I?    8     J?    ff 

j=     j:     j:     js      «" 

CJ         O         O          ^*        —  * 

Ilil! 

THE  PRACTICAL  PHYSICS  OF 


The   following   figure   shows  these  results  in  graphic  form, 
arranged  in  the  order  of  the  rates  of  evaporation. 


Date,   (1895  ) 

Duration  of  trial. 

Lhs.  of  water  evaporated  per  Ib   of  coal  from 
and  at  212* 


Lbs.  of  water  evaporated  per  Ib.  of  coal  under 
actual  conditions         


Steam  pressure  in  Boiler,  above  atmosphere .. 


Total  coal  burnt  per  hour, 


Ibs. 


Total   water   evaporated    per   hour   from    and 


at  212' 


Ibs. 


Feed  temperature.  Fahrt 
Lbs.  of  coal  burnt  per  sq    foot  of  grate 


I  >T      f ' 

•"       •'*'"       "^     '' 


FIG.  313. 


Professors  Kennedy  and  W.  C.  Unwin  conducted  trials  of  a 
Niclausse  boiler  at  Thames  Ditton  in  1894,  and  their  report  is 
attached  to  Mr.  Robinson's  paper.  The  outer  tubes  of  the 
boiler  were  3'22ins.  diameter  and  7  feet  long  ;  the  inner  tubes 


THE  MODERN  STEAM  BOILER. 


571 


were  i^ins.  diameter  and  nearly  the  same  length.  The  total 
external  tube  surface  in  the  boiler  was  649  square  feet.  The  trial  of 
1 2th  May  was  specially  to  ascertain  how  far  the  boiler  could  be 
forced  without  appreciable  priming  taking  place.  The  tests 
showed  that  the  priming  on  all  the  trials  was  practically  negli- 
gible in  amount.  The  following  Table  gives  the  results  of  the 
three  trials  : — 

TABLE  CVI. 


Date  of  Trials,  1894. 

April  10. 

April  n. 

May  12. 

Duration  of  trial  hours 

7-27 

7-40 

2'95 

Barometer  (mean)  ins. 

30-I4 

29-94 

30-09 

Total  water  evaporated  ...          Ibs. 

16,000 

l6,OOO 

12,134 

Total  coal  burnt    „ 

1,845 

I,84I 

1,422 

Carbon  value  of  coal  used 

0-956 

0-956 

— 

Total  feed  water  per  Ib.  of  coal  Ibs. 

8-67 

8-69 

8-53 

Total  feed  water    per    Ib.  of   coal 
from  and  at  212°  F.  ...          Ibs. 

10-47 

10-50 

10-34 

Total  feed  water  per  Ib.  of  carbon 
value  from  and  at  212°  F.  Ibs. 

10-95 

10-98 

10-82 

Coal  burnt  per  sq.  ft.  grate  surface 
per  hour 

I3-5 

I3-3 

25-6 

Feed    water    per    sq.    ft.     heating 
surface 

3'39 

3'33 

6'34 

Feed  water  per  cubic  foot  of  boiler 
and  boiler-setting  per  hour     ... 

2-61 

2'57 

4-88 

Mean  steam  pressure  above  atmo- 
sphere, Ibs.  per  sq.  in. 

I58-6       . 

159-6 

144'  3 

Mean  steam  pressure  absolute,  Ibs. 
per  sq.  in. 

I73-4 

I74'3 

I59-I 

Mean    temperature  of  feed    water, 
deg.  F. 

60-3 

603 

55-o 

Mean  temperature  of  air,  deg.  F.  .  .  . 

67-4 

67-6 

62-3 

Mean     temperature     of      chimney 
gases,  deg.  F. 

5117 

502-7 

732-0 

The  moisture  in  steam  was  determined  for  the  first  two  trials 
by  a  wire-drawing  calorimeter,  and  was  found  to  be  a  mean  of 
i.i  per  cent,  for  the  first,  and  ro  per  cent,  for  the  second. trial. 


57* 


THE  PRACTICAL  PHYSICS  OF 


The  figures  for  utilisation  of  the  heat  in  each  pound  of  coal, 
based  upon  an  estimated  thermal  value  for  the  coal  of  13860 
heat  units  as  calculated  from  an  ordinary  analysis,  or  from 
calorimeter  experiment,  are  given  in  the  following  Table  : — 


TABLE  CVII. 


Apri 

1   10. 

Apri 

In. 

Thermal 
Units. 

Percent- 
ages. 

Thermal 
Units. 

Percent- 
ages. 

Heat  utilised  in  formation  of 
steam              

Heat  lost  by  imperfect  combus- 
tion (formation  of   carbonic 
oxide) 

10,110 

CQI 

72-94 
3'6l 

10,136 
185 

73*ii 

I'33 

Heat  lost  by  carbon  left  in  ash  . 

Heat  carried  away  by   waste 
gases 

133 

2  327 

0*96 
l6'7O 

136 

2,4.3S> 

0^8 

I7-C6 

Heat    lost     by    radiation    and 
otherwise  unaccounted  for  ... 

789 

570 

968 

7-02 

Thermal  value  of  coal  as  de- 
termined by  experiment     ... 

13,860 

1  00'  00 

13,860 

1  00'  00 

In  the  trial  of  May  12,  the  heat  utilised  in  steam  formation 
amounted  to  9970  units  or  71-9  per  cent. 

In  M.  Duchesne's  paper  it  is  stated  that  the  Niclausse  boilers 
of  the  "  Menhir  "  worked  for  7000  hours  without  requiring  to 
be  cleaned  ;  and  that  those  of  the  tf  Friant "  have  worked  with 
a  consumption  of  176  kilogrammes  coal  per  metre  carre  of  grate 
surface  per  hour  without  difficulty  for  four  consecutive  hours, 
and  without  showing  flame  at  the  chimneys.  The  rates  of 
evaporation  at  different  rates  of  combustion  of  coal  were  ascer- 
tained to  be  as  follows  : — 

Kilogrammes  of  coal  burned  per  metre  carre  grate  surface  per 
hour  (ash  included)  : — 

100  150          200         250          300          350          400 

Kilogrammes  water  evaporated  per  unit  of  coal  at  these  rates 
(water  and  steam  reduced  to  100°  C.) 

11-850       10-860      9*914      9'339       8734      8-214      7*500 


THE  MODERN  STEAM  BOILER.  573 

These  evaporative  trials  were  continued  during  four  hours. 
Trials  at  a  rate  of  combustion  of  400  kilogrammes  coal  per  metre 
carre  grate  surface  per  hour  were  made  and  continued  for  ten 
hours,  the  air  pressure  being  20  mm.,  without  damage.  The 
diameter  of  the  tubes  was  40  mm.,  and  tubes  of  82  mm.  have 
stood  the  same  test. 

A  careful  record  of  the  performances  of  the  tubulous  boilers 
in  the  French  Navy  prior  to  1895,  and  a  trenchant  criticism  of 
various  features  of  their  construction  and  working  at  that  time, 
will  be  found  in  a  paper  by  Mr.  John  K.  Robison,  Assistant 
Engineer  in  the  U.S.  Navy,  read  before  the  American  Society  of 
Naval  Engineers  and  published  in  their  journal,  from  which  it 
was  republished  in  Engineering,  Vol.  lx.,  pp.  555,  587,  617,  682 
and  749.  Mr.  Robison  indicates  the  good  and  bad  qualities  of 
Belleville,  Lagrafelor  D'Allest  and  Niclausse  boilers,  and  evidently 
thinks  more  highly  of  the  two  latter  than  of  the  former. 

Of  trials  of  water-tube  boilers  in  the  German  Navy  there 
are  no  accounts  published  in  English,  but  articles  on  that 
subject  have  appeared  in  the  Zeitschrift  des  Vereines  Deutschet 
Ingenieure  of  nth  and  i8th  September,  1897  ("Versuche  in 
der  Deutschen  Kriegsmarine  mit  Wasserrohrkesseln "),  and 
on  the  Buttner  Water-tube  Boiler  in  La  Revue  Technique  of 
loth  September,  1897. 

Moshet  Boiler. — A  Mosher  boiler  gave  the  following  results  on 
an  eight-hours  trial  with  natural  draught  with  Pocahontas  semi- 
bituminous  coal. 

Coal  per  square  foot  of  grate  per  hour          7-1  Ibs. 

Water  evaporated  per  Ib.  of  coal       ...         9*12  Ibs. 

Air  supplied  per  Ib.  of  coal      304  cub.  ft. 

Temperature  of  gases  at  base  of  funnel         442°  Fahr. 

Draught  at  base  of  funnel        ...         3  in. 

Wetness  of  steam  as  measured  by  calorimeter  1-5  per  cent. 

Percentage  of  ashes  7  per  cent. 

Quantity  of  water  evaporated  in  ash-pit  during  the 

whole  trial        90*2  Ibs. 

The  principal  dimensions  of  the  boiler  were  : — 

Grate  area  ...  ...  ...     33  sq.  ft. 

Heating  surface      ...  ...  ...1108       „ 

Ratio  of  grate  to  heating  surface         ...     33*6 

Load  on  safety  valve  ...  ...  185  Ibs. p.  sq. in. 


574 


THE  PRACTICAL  PHYSICS  OF 


The  heat  utilisation  was  as  follows  :  — 

Heat  utilised  in  evaporating  water      ...  76-0  per  cent. 

Heat  lost  in  the  funnel          ...  ...  13-0       ,, 

Heat  lost  in  radiation  ...  ...  9-1       „ 

Heat  lost  in  cinders  and  evaporation  of 

water  in  the  ashpan       ...  ...  1*0       ,, 


Total  heat  of  combustion  ...   loo-o 

"  Clyde  "  Boiler.—  The  following   are   the   results  of  trials  of 
three  boilers  of  Messrs.  Fleming  and  Fetguson's  design  :  — 

TABLE  CVIII. 


No.  I. 

No.  2. 

No.  3. 

Grate  area 

o*  sq.  ft. 

20  sq.  ft. 

4S'8  sq.  ft. 

Heating  surface 

?2     *r*l< 

540  sq.ft. 

630  sq.  ft. 

if.*}      V       wJVJ 

i,65osq.  ft. 

Coal  consumed  per  square  foot  of 
grate  per  hour       

24-8  Ib. 

20-3  Ib. 

30-3  Ib. 

Total  coal  consumed  per  hour 

236  Ib. 

406  Ib. 

1,391  Ib. 

Water  evaporated  per  hour  

2,040  Ib. 

3,500  Ib. 

9,812  Ib. 

Water  evaporated  per  hour   from 
and  at  212°  F  

2,468  Ib. 

4,260  Ib. 

n,345  Ib. 

Water  evaporated  per  Ib.  of    coal 
from  and  at  212°  F. 

10-43  Ib. 

10-5  Ib. 

8*15  Ib. 

Water  evaporated  per  Ib.  of   com- 
bustible      ... 

11*15  Ib. 

11*25  Ib. 

87  Ib. 

Water  evaporated  per  square  foot 
of  grate  per  hour  

260  Ib. 

• 
213  Ib. 

247  Ib. 

Water  evaporated  per  square  foot 
of  heating  surface  per  hour  from 
and  at  212°  F  

4-5  Ib. 

67  Ib. 

6-8  Ib. 

Quality  of  coal  used           

Welsh 

Welsh 

Scotch 

Draught  natural  on  all  trials. 

This  boiler  is  fitted  in  the  s.s.  "  Aberdeen,"  a  vessel  owned  by 
the  Canadian  Government,  and  has  given  satisfaction.  The 
generating  tubes  are  2\  inches  diameter,  the  steam  cylinder 
being  of  sufficient  diameter  to  permit  of  their  being  wholly 
withdrawn  into  it  when  any  tubes  require  to  be  replaced. 


THE  MODERN  STEAM  BOILER. 


575 


The  following  are  the  proportions  of  three  different  sizes  and 
arrangements  of  the  tubes  and  chambers  proposed  by  Messrs. 
Fleming  and  Ferguson  :— 


Boiler  with  3 
furnaces. 

Boiler  with  6 
furnaces 
(double-ended). 

Boiler  with  4 
transverse 
furnaces. 

Grate  area,  square  ft.           

50                       138 

165 

Heating  surface,  square  ft  

I450'5 

4801 

5000 

Ratio  of  heating  surface  to  grate  ... 

28-98 

3479 

30J 

Total  weight  with  water  but  without 
funnel,  tons           

30 

75 

no 

Working  pressure,  Ibs.  per  sq.  in.... 

220 

200 

250 

Mumford's  Boiler. — Mumford's  water-tube  boilers  have  given 
satisfactory  results  in  the  trials  on  H.M.S.  "  Salamander."  This 
vessel  is  of  the  same  type  as  the  "  Sharpshooter,"  the  first  fitted 
with  the  Belleville  boiler,  and  since  then  the  class  has  been 
utilised  for  trying  various  systems  of  tubulous  generators,  the 
Babcock  and  Wilcox,  Niclausse,  and  the  Du  Temple,  as  well  as 
the  Mumford.  The  boilers  on  an  eight-hours'  natural  draught 
trial  gave  sufficient  steam  for  2575  I. H. P., and  although  they  were 
only  required  to  give  3500  I.H.P.  under  forced  draught,  the 
power  was  actually  4114  I.H.P.,  which  was  got  with  2'6  inches 
of  air  pressure  in  the  stokehold.  The  boilers,  of  which  there 
are  four,  have  180  square  feet  of  grate  area  and  8000  square 
feet  of  heating  surface,  so  that  the  power  is  equal  to  a  little  over 
23  horse-power  per  square  foot  of  grate,  while  there  was  barely 
two  square  feet  of  heating  surface  for  each  unit  of  power  de- 
veloped, both  results  being  very  good,  even  for  an  express  boiler. 

Haythotn  Boiler. — Of  other  water-tube  boilers  which  have 
been  fitted  in  steamers,  the  Haythorn  boiler  is  one  of  consider- 
able promise,  judged  from  the  results  of  trials  which  have  been 
made.  The  first  of  these  boilers  was  made  and  tried  as  a  land 
boiler,  of  which  an  illustration  will  be  found  in  Engineering,  Vol. 
lx.,  p.  680. 

The  heating  surface  of  the  boiler  was  430  square  feet,  and  the 
grate  area  6'8  square  feet,  the  ratio  between  these  two  being  63  to  I. 

The  following  are  the  results  of  the  trials  : — 


576 


THE  PRACTICAL  PHYSICS  OF 


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Chimney  draught  by  water  g 
Air  pressure  under  fire,  forcei 

Air  temperature,  Fah.  ... 
Mean  feed  temperature,  Fah. 

Coal  consumed  per  hour,  Ibs. 

Coal  consumed  per  hour,  per 

Water  evaporated  per  hour,  11 

Water  evaporated  per  hour  p 

Equivalent  evaporation  from 

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Mean  steam  pressure,  Ibs.  pei 

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Quality  of  steam 

THE  MODERN  STEAM  BOILER.  577 

Subsequently  two  boilers  were  fitted  in   the  paddle  steamer 
"  Meg  Merrilies,"  the  following  being  the  dimensions  of  each  : — 
Diameter  of  tubes,  2  ins.  and  3^-  ins.,  reduced  to  2  ins. 
Pitch  of  tubes,  3^  ins.  by  3^  ins. 
Longest  tube,  14  ft.  3  ins.  between  ferrules. 
Shortest  tube,  9  ft.  i  in.  between  ferrules. 
Mean  tube,  n  ft.  8  ins.  between  ferrules. 
Number  of  2  in.  tubes  in  boiler,  216. 
Numbes  of  3^  in.  tubes  in  boiler,  54. 
Total  number  of  tubes,  270. 

Number  of  tubes  in  each  element,  30  ;  number  of  elements,  9. 
Effective  heating  surface  of  tubes  in  one  element,  191*3  sq.  ft. 
Total  heating  surface  of  tubes  in  boiler,  17217  sq.  ft. 
Total  grate  surface  in  one  boiler,  30*5  sq.  ft. 
Ratio  of  heating  to  grate  surface,  56*4  to  I  sq.  ft. 
Weight  of  one  element,  excluding  water,  13  cwts. 
Weight  of  one  boiler,  excluding  water,  13*2  tons. 
Weight  of  water  in  one  boiler,  2*35  tons. 
Total  weight  of  boiler,  including  water,  15*55  tons. 
WTorking  steam  pressure,  200  Ibs.  per  square  inch. 

The  results  of  a  trial,  lasting  for  six  hours,  of  these  boilers  on 
board  the  steamer  while  cruising  in  the  Firth  of  Clyde  on  2ist 
December,  1898,  are  given  in  the  following  tabular  statement  : — 

TABLE  CX. 

EVAPORATIVE    TEST   OF   THE    HAYTHORN   WATER-TUBE 
BOILERS    OF   P.S.    "MEG   MERRILIES." 

BOILERS.     (Two  Hciythorn  Water-Tube  Boilers.} 

Total  heating  surface 3444  square  feet. 

Total  grate  area            ...         ...         ...         ...         ...  61           ,, 

Heating  surface 

Rati°— Grate  area  56'4       " 

Mean  steam  pressure  above  atmosphere     186  Ibs.  • 

TEMPERATURES. 

Mean  funnel  temperature,  about  ...  ...  ...  600° 

Mean  temperature  of  stokehold  ...  ...  ...  68° 

Mean  temperature  of  feed  water  ...  ...  ...  127'4° 

DRAUGHT. 

Mean  funnel  draught  below  atmosphere     ...         ...         -35"  water. 

Mean  air  pressure  in  stokehold  above  atmosphere  '55"      „ 

Total  -9"      „ 


578  THE  PRACTICAL  PHYSICS  OF 

TABLE  CX.  continued. 

COAL.— Quality,  Welsh. 
Analysis — 

Carbon- 83-63  per  cent. 

Hydrogen          ...         ...         ...         ...         ...         ...  37°         » 

Oxygen 4-48         „ 

Nitrogen            ...         ...         ...         ...         ...         ...  '99         ,, 

Sulphur  ...         ...         ...         ...         ...         ...         ...  7           ,, 

Water 1-28 

Ashes      5-22    o    „ 

Theoretical  evaporative  power  14-5  Ibs.  water  from  and  at  212°. 

ANALYSIS  OF  SMOKE. — Mean  of  Three  Samples. 

By  Volume.      By  Weight. 

Carbonic  acid 8-17  I2'i 

Carbonic  oxide             ...         ...         ...         ...  'I  '09 

Hydrocarbons  ... 

Oxygen 10-3  11-03 

Nitrogen            81-43  76-78 


100-00  100-00 

COAL. 

Total  used  in  6  hours  3  minutes       9321  Ibs. 

Used  per  hour  ...  ...  ...  ...  ...  ...  I541  ,, 

„  per  square  foot  of  grate  25-26  ,, 

„  „  of  heating  surface  ...  '447,, 

ASHES. 

Total  ashes  for  6  hours  3  minutes 95  Ibs. 

,,     clinker  for  6  hours  3  minutes 482    ,, 

Total          577    „ 

Ashes  and  clinker  per  hour    ...         ...         ...         ...  95    >, 

,,                  percentage  of  coal          6'2  per  cent. 

WATER. — Measured  for  5  hours  47  minutes  u  seconds. 

Total  quantity  from  hotwell 80943  Ibs. 

Supplementary  from  tanks 2133    „ 

Total          83076    „ 

Water  per  hour           ...         ...         ...         ...         ...  14345    ,, 

,,           ,,          per  square  foot  grate          ...         ...  235    ,, 

,,           ,,                     ,,                 heating  surface  ...  4- 165    ,, 
-Water  evaporated  per  Ib.  of  coal  from  temperature 

of  feed  water        9'3O9    „ 

Water  evaporated  per  Ib.  of  coal  from  and  at  212°  10*62    „ 

An  independent  dry  steam  test  was  made  by  means  of  a  "  Barrus  "  Wire- 
drawing Calorimeter.  This  test  gave  the  mean  dryness  factor  at  -924,  or 
only  2'6  per  cent,  of  water  in  the  steam. 

From  above  results  the  efficiency  of  these  boilers  is — 
Actual  evaporative  power  per  Ib.  of  coal  from  and  at  212° 10-62 per 

Theoretical  evaporative  power  of  coal  from  and  at  212°  14-5  cent. 
Also  water  evaporated  per  Ib.  of  carbon  value  from  and  at  212°  iro6  Ibs. 


THE  MODERN  STEAM-BOILER. 


579 


The  three  boilers  fitted  in  the  paddle  steamer  "  Lorna  Doone  " 
in  May,  1899,  had  some  slight  improvements  in  detail,  such  as 
the  formation  of  a  combustion  space  by  means  of  an  extra  row 
of  tubes  between  the  grate  .and  the  main  body  of  the  boiler 
tubes. 

The  following  are  their  principal  dimensions  : — 

Diameter  of  tubes,  2  ins.  and  3^  ins.,  reduced  to  2^  ins. 

Pitch  of  tubes,  3^  ins.  by  3^  ins. 

Longest  tube,  14  ft.  6  ins.  between  ferrules. 

Shortest  tube,  8  ft.  4  in.  between  ferrules. 

Mean  tube,  n  ft.  5  in.  between  ferrules. 

Number  of  2  in.  tubes  in  one  boiler,  264. 

Number  of  3^  in.  tubes  in  one  boiler,  96. 

Total  number  of  tubes  in  one  boiler,  360. 

Number  of  tubes  in  one  element,  30  ;  numberfcf  elements,  12. 

Effective  heating  surface  of  tubes  in  one  element,  200  sq.  ft. 

Total  heating  surface  of  tubes  in  one  boiler,  2,400  sq.  ft. 

Total  grate  surface  in  one  boiler,  42*4  sq.  ft. 

Ratio  of  heating  to  grate  surface,  56*6  to  I  sq.  ft. 

Weight  of  one  element,  excluding  water,  14  cwts. 

Weight  of  one  boiler,  excluding  water,  18*6  tons. 

Weight  of  water  in  one  boiler,  2'8  tons. 

Total  weight  of  boiler,  including  water,  21*5  tons. 

Working  steam  pressure,  160  Ibs.  per  sq.  inch. 

On  trial  these  boilers  gave  the  following  results  : — 


TABLE  CXI. 

P.  S.  "LORNA  DOONE"  OF  THE  SOUTHAMPTON,  ISLE  OF  WIGHT,  AND 
SOUTH  OF  ENGLAND  R.  M.  S.  P.  COY. 


Date  of 
Voyage. 

Total 
Dis- 
tance 
Tra- 
velled. 

Duration 
of 
Voyage. 

Weights  on  board. 

Average 

I.  H.  P. 

Devel- 
oped. 

Quality 
of  Coal 
used. 

Coal  used 
per  mile 
run. 

ll,|l 

u*n 

Total  coal 
used  in 
24  hours. 

Lbs.  of 
Coal 
per 

I.  H.  P. 

Type  of 
Boiler 
used. 

Coal  22  tons 

£*.* 

a*  _ 

Water  in)  e 

204  Ibs. 

•*  (-: 

£  ^ 

22nd 
Aug., 
1899 

170 
knots 

H.   M.   S. 
12  33  10 

Tanks.  (  5    " 
Passsen- 
gers   ...35    „ 

1,411 

Inferior. 

gross  i.e. 
includ- 
ing 

rii 

3  *"ot! 

£-0 

£g 

1-96 

Hay- 
thorn 
water- 

banking 

c     -1 

o 

tube. 

Total  62    „ 

of  fire. 

§M§ 

£10 

^     0 

H" 

U2 


580  THE  PRACTICAL  PHYSICS  OF 

Some  very  instructive  trials  to  determine  the  relative  value  for 
evaporation  of  successive  tiers  of  tubes  from  the  bottom  row 
upwards  in  such  boilers  as  the  Niclausse,  and  the  advantage  to 
be  gained  by  adding  heating  surface,  either  in  rows  of  boiler 
tubes  or  in  economisers,  were  carried  out  by  Messrs.  Niclausse 
in  Paris.  They  constructed  a  special  boiler  containing  12  rows 
of  tubes,  two  in  each  row,  placed  side  by  side.  Each  row  de- 
livered its  steam  separately,  and  was  separately  supplied  with 
water  of  measured  quantity.  The  tests  were  carried  out  at  rates 
of  combustion  varying  from  lolbs.  up  to  6ilbs.  per  square  foot  of 
grate,  and  the  proportionate  evaporation  in  each  row  of  tubes 
was  maintained  almost  exactly  at  all  the  different  rates  of  com- 
bustion. The  lowest  rowr,  directly  over  the  fire,  evaporated 
nearly  one  quarter  of  the  whole,  and  the  first  three  rows,  having 
7-5  square  feet  of  heating  surface  to  one  square  foot  of  grate, 
evaporated  nearly  one  half.  (See  pp.  187 — 191  ante). 

The  first  six  rows,  with  a  surface  ratio  of  fifteen  to  one, 
evaporated  nearly  two-thirds  of  the  whole.  The  last,  or  upper- 
most row  evaporated  about  3!  per  cent.,  and  the  law  of  decreas- 
ing efficiency  under  the  conditions  of  the  trials  was  readily 
deducible,  enabling  the  value  of  any  additional  surface  to  be 
estimated. 


TWO   TESTS   OF    SIMPSON    AND     RODMAN'S    FLASH 

BOILER. 

PARTICULARS   OF   GENERATOR. 

Weight  of  generator,  645  Ibs. 

Weight  of  regulating  drum,  98  Ibs. 

Number  of  members,  12. 

Tubes  per  member,  2. 

Length  indented  per  tube,  2ft.  6in. 

Pitch  of  indent,  3^  in. 

Heating  surface  indented,  46  square  feet. 

Joints,  the  "  Haythorn  "  differential  joint. 

Hydraulic  (cold)  test  for  joints,  750  Ibs.  per  square  inch. 

Thermometer  used,  Mercury,  with  nitrogen  chamber  reaching 

to  900°  Fah.,  bulb  depending  ift.  6in.  into  drum. 
Grate  area,  2|  square  feet. 
Fire  bars,  ^-in.  wide  ;  air  spaces,  ^-in.  wide. 


THE  MODERN  STEAM  BOILER.  581 

LIGHTING  UP  TEST. 

Fire  made  up  from  plain  kindling  wood  and  7'o  seam  coal. 
Fire  lit  at  3.30  p.m. 
Steam  for  blower  at  3.40  p.m. 
400°  Fah.  in  drum  at  3.55  p.m. 
Ready  for  work  at  4  p.m. 

TABLE  CXI  I. 

FIRST   TEST.      DURATION    THREE    HOURS. 
FUEL   USED — FURNESS  COKE. 

Starting. — Fire  lit  and  boiler  blown  out  for  one  hour,  the  fire  then  drawn  out 

and  thrown  aside.      Temperature  of  boiler  taken — 380°  Fah. — fresh  firing 

applied,  and  test  proceeded  with. 


ist  Hour. 

2nd  Hour. 

3rd  Hour. 

H.M. 

Deg. 
Fah. 

Ibs. 

H.M. 

Si;:  «- 

H.M. 

Deg. 
Fah. 

Ibs. 

Times    of     stoking    and    tem- 

perature   at    each    stoking 

taken    before    fire    door    is 

opened 

11.25 

380° 

12.25 

500° 

1-25 

500° 

11-35 

600° 

12-35 

600° 

1-37 

600° 

"•45 

730° 

12-45 

730° 

1-45 

650° 

"•55 

500° 

12.55 

500° 

1-55 

700° 

12.  5 

500° 

i.  5 

500° 

2-    5 

730° 

12.15 

500° 

MS 

55o° 

2.15 

600° 

Times  of  clinkering,   cleaning, 

etc 

1.25 

Fuel  weighed  out  at  start 

57 

64 

78 

in  at  finish 

— 

- 

— 

„     used  

57 

64 

7« 

Gross  weight  water  and  tank  at 

start      

500 

488 

412 

Gross  weight  water  and  tank  at 
finish 

234 

136 

36 

Weight  of  water  evaporated  ... 
Pressure  worked  at  per  square 

266 

352 

376 

IOO 

IOO 

IOO 

Temperature  of  feed  water     ... 

70° 

70° 

70° 

Evaporation  per  Ib.  fuel  u-.ed... 

466 

5"  5 

4-82 

„           per    square    foot 
heating  surface        

578 

7-65 

8-17 

Combustion    per    square    foot 

207 

23-27 

28-36 

Average  temperature    
Degrees     of    superheat    above 
saturation       

535° 
197° 

5630 

225° 

630° 
292° 

Water  pumped  through  at  2.25  to  reduce  temperature  to  380°. 
REMARKS  :— Weight  of  ash  not  taken,  being  very  slight. 
Nozzle  in  blast  pipe  J"  diameter. 
Evaporation  per  Ib.  fuel  is  taken  as  shown  at  pressure  and  temperature. 


582  THE  PRACTICAL  PHYSICS  OF 

TABLE  CXIII. 

SECOND   TEST.     DURATION   THREE    HOURS. 
FUEL — ANTHRACITE. 

Starting  as  in  Test  I.         Temperature  550°  Fah. 


ist  Hour. 

2nd  Hour. 

3rd  Hour. 

H.M. 

Fah. 

Ibs. 

H.M. 

Fah. 

Ibs. 

H.M. 

Fah. 

Ibs. 

Times  of  stoking  and  tempera- 
ture        

9.40 

550° 

10.40 

500° 

ii-55 

450° 

9-5° 

780° 

10.45    450° 

12.    O 

550° 

10.   O 

550° 

10.50    450° 

12.  5 

700° 

10.  5 

480° 

10.55    500° 

12.15 

700° 

IO.IO 

560° 

ii.  o     510° 

12.25 

55o° 

10.15 

560° 

"•  5 

375° 

12.35 

530° 

IO.2O 

460° 

1  1.  10     400° 

12.45 

530° 

10.25 

460° 

11.15  '•  500° 

10.30 

460° 

11.20        550° 

10.35 

460° 

11.25 

550° 

11.30 

550° 

Times  of  clinkering  and  clean- 

ii.  5 

\r\ff 

IO.4O 

11.40 

Fuel  weighed  out  at  start 

131 

136 

69 

„         „         in  at  finish 

53 

6y 

- 

„    used  

78 

67 

69 

Weight  of  Ash    

30 

30 

30 

Nett  fuel  consumed      

48 

37 

39 

Gross  weight  of  water  and  tank 

at  start  

468 

500 

500 

Gross  weight  of  water  and  tank 
at  finish 

126 

189 

196 

Weight  of  water  evaporated  ... 

342 

3H 

304 

Pressure  worked  at  per  square 

inch        

IOO 

IOO 

IOO 

Evaporation   per  nett  ,lb.   fuel 

used        

7-12 

8'2 

7  '97 

Evaporation    per   square    foot 
heating  surface           

r  o 

, 

6-7 

6-  6 

Combustion    per    square    foot 

grate      

17'  5 

I3'3 

14-  2 

Average  temperature     
Degrees    of    superheat    above 
saturation         

532° 
194° 

4850  , 
147° 

572° 
234° 

REMARKS  :— The  fire  bars  were  evidently  not  suitable  for  burning  Anthracite,  as  the  amount 

of  ash  it  excessive. 
The  bars  also  choked  up  badly.        Nozzle  in  flue  J"  diameter. 


THE  MODERN  STEAM  BOILER.  583 

Comparison  of  Results. — It  is  much  to  be  regretted  that  there 
are  no  reports  extant  of  the  work  performed  by  such  boilers  as 
those  of  theJiighly  interesting  class  introduced  early  in  last  century 
in  connection  with  road  vehicles,  and  also  by  some  of  later  date, 
such  as  the  boilers  of  Dr.  De  Laval  in  Sweden,  and  one  or  two 
others.  A  comparison  of  results  would  be  of  great  use  in  determin- 
ing the  relative  value  of  different  arrangements  of  heating  surface 
and  other  elements  of  boiler  design,  as  woiked  under  ordinary 
conditions  of  steam-raising.  As  we  have  pointed  out  in  Chap.  IV., 
the  value  of  experiments  made  to  determine  the  capacity  of  metal 
surfaces  for  heat  transmission  has  been  greatly  interfered  with  by 
reason  of  the  actual  design  of  the  apparatus  used.  Hence  such 
calculations  as  those  of  M.  Bertin  (in  "  Marine  Boilers,"  pp.  126- 
129)  which  are  founded  upon  the  formula  deduced  from  Mr. 
Blechynden's  experiments  cannot  be  relied  upon  for  any  general 
application.  Enquiry  into  the  results  actually  obtained  in  Ibs. 
of  water  evaporated  per  square  foot  of  heating  surface  in  various 
boilers,  only  shows  that  these  results  are  not  concordant,  and 
that  therefore  \ve  have  not  arrived  at  the  time  when  a  rule  or 
formula  can  with  safety  be  deduced.  For  instance,  many  Bab- 
cock  and  Wilcox  land  boilers  show  an  evaporation  of  not  more 
than  27  Ibs.  of  water  per  square  foot  of  heating  surface  per 
hour  ;  in  the  diagram  of  boiler  trials  at  Philadelphia  in  1876 
(p.  527  ante)  only  five  out  of  thirteen  boilers  show  an  evaporation 
above  the  average  of  2'86  Ibs.  per  square  foot  of  heating  surface  ; 
one  of  these  five,  however,  showed  10*585  Ibs.  A  "  Glasgow  " 
water-tube  boiler  has  shown  61bs.  per  square  foot  of  heating 
surface  per  hour,  and  instances  of  other  boilers  giving  figures  of 
from  17  up  to  20*05  Ibs.  will  be  found  in  this  chapter.  The 
latter  figure  was  credited  to  locomotive  boilers  in  Italian  torpedo 
boats,  but  it  has  been  reached  on  special  forcing  trials  with 
either  Yarrow  or  Thornycroft  forms  of  water  tube-boilers. 
The  Niclausse  boiler  of  the  "  Temeraire  "  showed  from  4-5  to 
15-9  Ibs.  on  trial.  The  special  boiler  designed  by  Simpson  and 
Boclman  for  motor-car  work  gave  on  trial  an  evaporative  rate  of 
9lbs.  per  square  foot  of  heating  surface,  and  the  boiler  of  De 
Laval  seems  to  have  done  more  than  this.  Professor  Watkinson 
announced  a  result  of  5olbs.  of  water  evaporated  per  hour  per 
square  foot  of  surface  in  an  experimental  boiler  of  new  design  ; 
and  we  have  the  figure  of  72lbs.  as  previously  given  for  the 


584  THE  PRACTICAL  PHYSICS  OF 

Niclausse  boiler  under  special  circumstances.  Now,  although  it 
is  true  that  these  results  were  not  always  obtained  under  the  best 
conditions  for  economical  working,  yet  they  throw  light  upon 
the  possibilities  of  steam  generation.  They  show,  moreover, 
that  we  must  aim  at  higher  rates  of  evaporation  than  have  been 
customary,  and  that  in  any  deduction  of  the  theoretically  possible 
we  must  take  into  consideration  such  results,  as  well  as  those  of 
C.  R.  Lang  and  of  Professor  Witz,  for  enlightenment  as  to  the 
rate  of  heat  transmission. 

Weight  and  Space  Occupied. — From  the  foregoing  tables  of 
results  many  figures  can  be  gathered  giving  the  weights  of 
various  boilers  relatively  to  a  standard  of  comparison  such  as  the 
I.H.P.  or  the  square  foot  of  grate  surface.  It  has  been  said  that 
"  the  real  coefficient  of  lightness,  the  weight  per  horse- power, 
is  equal  to  the  weight  per  square  foot  of  grate  surface  divided 
by  the  maximum  horse-power  per  square  foot  of  grate  surface, 
always  supposing  the  weight  of  steam  per  horse-power  required 
by  the  engines  to  be  a  constant  quantity,"  but  it  is  not  apparent 
why  the  engines  should  be  introduced  into  the  elements  of  a 
comparison  amongst  boilers.  It  would  surely  be  more  direct 
and  satisfactory  to  express  the  weight  of  the  quantity  of  water 
evaporated  from  and  at  212°  F.  per  hour  or  per  unit  of  surface 
by  the  boiler. 

Some  useful  figures  of  comparison  of  the  \veights  and  space 
occupied  by  tubulous  boilers  in  the  French  Navy  were  given  by 
Mr.  J.  K.  Robinson,  and  will  be  found  reprinted  in  Engineering, 
Vol.  lx.,  p.  750,  etc.  The  following  are  two  of  the  Tables 
given  : — 


THE  MODERN  STEAM  BOILER. 


585 


TABLE  CXIV. 


DETAILED  WEIGHTS  OE  BOILERS. 


D'Allest. 

Belleville. 

Xiclausse. 

Boilers  proper           

I3I-3 

!v 

14^5 

Uptakes 

67-0 

s6'o 

Accessories 

irS 

273-3 

6-6 

Grates  and  fittings    ... 

19-1 

. 

18-3 

Tools  and  spare  parts 

5-6 

8-1 

7-6 

Feed  pumps 

C'2 

11'  A 

C'2 

Tanks 

4'° 

8-0 

d'O 

Smoke  pipes 

I7'O 

2V:\ 

IQ'8 

Floor  plates  and  ladders 

9'0 

9'0 

9'0 

Fire-room  ventilators 

9-0 

9"0 

9'0 

Air  compressor         

2'5 

— 

Separator        

5'2 

— 

Water  in  boilers 

53'0 

16-0 

53-o 

Total  of  fire-rooms           

332-0 

365-0 

335'Q 

Total  of  engines  and  boilers 

757-0 

8oro 

760-0 

In  the  case  of  the  Niclausse  Boilers — which  were  those  of  the 
Friant,  the  actual  weight  of  the  boiler  as  delivered  \vas  329^0 
tons,  the  boiler  proper  having  weighed  202*61  tons  and  the 
uptakes  only  1076  ;  the  water  in  the  boilers  also  was  reduced  to 
46-18  tons. 


586 


THE  PRACTICAL  PHYSICS  OF 


The  dimensions  of  the  boilers   are    given    in    the   following 
Table  :— 


TABLE  CXV. 


DIMENSIONS  OF  THE  BOILERS. 


D'Allest. 

Belleville. 

Niclausse. 

Number  of  fire-rooms 

3 

3 

3 

,,         ,,  boilers  ... 

2O 

24 

20 

,,         ,,  furnaces  per  boiler     ... 

I 

i 

I 

Length  of  grate,  ft.  and  ins. 

6  ft.  8  in. 

4  ft.  7  in. 

6  ft.  8  in. 

Width  of  grate,  ft.  and  ins. 

5  ft.  4^  in. 

7  ft.  oin. 

6  ft.  o  in. 

Total  grate  surface,  sq.  ft  

.732 

755'2 

782-8 

Total  heating  surface,  sq.  ft. 

19,451 

2i,594 

23,338 

Ratio  of  H.S.  to  G.S. 

26-6 

28-6 

29-8 

Outside  diameter  of  tubes,  ins. 

3-25 

3-23 

3-23 

Inside  diameter  of  tubes,  ins. 

2-91 

2-86  &  2-60 

2'97 

Length  of  tubes,  ft.  and  ins. 

7  ft.  9  in. 

6  ft.  4  in. 

5  ft.  8*  in. 

Diameter  of  circulating  tubes,  ins.... 

— 

— 

lT°6 

Number  of  tubes  in  vertical  row  ... 

10 

9 

9 

Weight  of  water,  tons 

53 

16-2 

46-2 

Volume  of  steam  space,  cubic  ft.  ... 

1,879 

784 

830 

Boiler  pressure,  Ibs.  per  sq.  in. 

214 

242 

214 

Pressure  at  engines  ... 

170 

170 

170 

Comparison  of  the  space  occupied  by  modern  forms  of  shell 
boilers  of  the  Scotch  and  locomotive  types  with  that  required  by 
tubulous  boilers  is  afforded  by  the  following  two  Tables  taken 
from  M.  Bertin's  work  on  "  Marine  Boilers."  Fully  detailed 
tables  of  weights  will  be  found  in  that  work  at  pages  218  and 
355- 


THE  MODERN  STEAM  BOILER. 


587 


TABLE  CXVI. 


Boilers. 

Name  of  Ship. 

Horizontal  projection  in 
square  feet. 

Ratio 
c 
g 

of  the  boiler  c. 

of  the  grate  g. 

2  furnaces      

Sfax           | 

102-39 
110-85 

42-95 

2-37I 

Single- 

1  2  furnaces     

Manche     

92-17 

43  "8l 

2-104 

ended 

•{  3  furnaces     ... 

Amiral  Baudin     

106-3 

63-61 

1-671 

boilers. 

3  furnaces     

/ 
(. 

150-16 
I44-63 

73-74 
70-29 

2036 
2-058 

t.  3  f  rnaces.(old  boilrs.) 

s.s.  Bretagne        

145-12 

.    70-07 

2-O7I 

3  furnaces  (common 
J      combsn.  chmbrs.) 

Cecile         | 

252-75        I 
250-0          / 

142-09  | 

1-779 
1-759 

Double- 

I  3  furnaces 

Capitaine  Prat     

266-57 

136-76 

I  "935 

ended 

-;  4    furnaces    (2  com- 

D'Entrecasteaux   

28O-IO 

194-28 

1-441 

boilers. 

bustion  chmbrs.)... 

1  4   furnaces  (2    com- 

Columbia   

329-33 

168-01 

1-960 

bustion  chambrs.) 

Hoche        

216-62 

70-00 

3-004 

Admiralty 
boilers. 

(3  furnaces 
2  furnaces     
2  furnaces     

Matsou-Sima       
Dupuy  de  Lome  
Suchet       

183-91 
201-48 
18961 

57-15 
46-93 

2-848 
4-040 

2  and  3  furnaces     ... 

Linois         ...         ...          \ 

185-06 
161-52 

71-20 

' 

(i  furnace  ...         | 

Torpedo  boats  Xos.  105  f 
to  114     \ 

94-81 

24-76 

3-830 

L°S±'e^f™-...     { 

Torpedo  boats  Nos.  127  f 
to  129     \ 

116-03 

30-35 

3-823 

1  i  furnace  

Bombe       

77-79 

19-37 

4-016 

\i  furnace  ... 

Acheron 

95-06                   19-16 

4-961 

TABLE  CXVI  I. 


Type  of  Boiler. 

Number  of 
furnaces. 

Name  of  vessel. 

Horizontal  projection  in 
square  feet. 

Ratio 
c 

of  the  boiler  c. 

of  the  grate  g. 

g 

( 

Alger      

Latouche-Tre- 

50-80 

3IH3 

1-62 

ville     

70-07 

43-38 

1-61 

Belleville       

i  furnace   -I 

Bugeaud 

54'89 

34-44 

1-59 

] 

Bouvet  

59^5 

35-52 

1-69 

I 

Charlemagne    } 
Gaulois          ...  J 

89-98 

57-37 

1-57 

Oriolle                                   1 

2  furnaces... 
i  furnace  ... 

Zouave  ... 
Torpedo  boats 

54-25 

31-43 

1-73 

I 

161-163 

41-97 

24-22 

i-73 

Bombe   

I07-IO 

50-59 

2"I2 

Jemmapes 

I38-52 

80-73 

172 

Chasseloup- 

D'Allest         

Laubat 

128-83 

68-89 

I-87 

Cassini   ... 

I33-45 

7793 

171 

Carnot    

167-92 

90-42 

i  86 

Xiclausse      

i  furnace   j 

Du  Chayla 
Friant     
Elan       

63-1 
266-31  . 
44-56 

34-4 
183-39 
•  21-42 

1-84 
1-45 
2-08 

Dragon  

78-36 

40-69 

192 

Du  Temple              

Averne   
Torpedo  boats 

75-75 

38-21 

1-98 

195-200 

112-48 

45'2i 

2-49 

Du  Temple-Normand 

i  furnace  ... 

Filibuster 

90-42 

3337 

271 

Torpedo  boats 

148,  149 

121-07 

35-74 

3'39 

Xormand 

Torpedo  boats 

182-185 

116-23 

3875 

3-oo 

Forban  ... 

128-83 

44X3 

2-92 

(Chateau-Ren- 

Xormand-Sigaudy  

ault     
Dunois  and 

239-7 

964 

2-48 

Lahire 

18985 

64-80 

2'93 

Guyot  (Indre)          

i  furnace  ... 

Jeanne  d'Arc    ... 

101-7 

4616 

2-19 

Thornycroft  

i  furnace   -j 

Veloce    
Coureur 

99-14 
112-38 

37-99 
38-10 

2-61 

2-95 

5^8  THE*  PRACTICAL  PHYSICS  OF 

Regarding  these  figures  M.  Berlin  has  remarked  that  the 
horizontal  space  required  by  a  boiler  may  be  expressed  by  the 
vertical  projection  of  its  horizontal  dimensions  to  the  grate  area. 

Thus  the  coefficient  of  floor  space  for  the  Niclausse  Boiler 
comes  out  lowest  at  1-5.  The  D'Allest  Boiler  17  to  r8,  and  the 
Belleville  Boiler  r6  to  17.  The  Du  Temple  coefficient  averages 
2-5  and  the  Normand  3.  Double-ended  cylindrical  boilers  have 
a  mean  coefficient  of  horizontal  floor  space  at  175  and  for  single- 
ended  boilers  it  reaches  2.  Boilers  of  the  navy  type  show  from 
2*6  to  4,  and  the  locomotive  pattern  goes  from  3-8  to  nearly  5. 

With  these  figures  may  be  compared  those  given  by  Sir.  A.  J. 
Durston  in  Table  CII.  on  page  561  ante. 

The  following  gives  the  total  weight  per  square  foot  of  grate 
surface  of  various  types  of  boilers  : — 

Cylindrical  boilers,  Admiralty  type   ...  ...  1*124  tons 

Single-ended  cylindrical  marine  boilers  ...  0-85  ,, 

Double-ended       ...  ...  ...  ...  0-814  ,, 

Locomotive  marine  boilers  for  ships  ...  0*96  „ 

Locomotive  marine  boilers  for  torpedo  boats...  0-549  » 

Belleville    Boiler       .  ...  ...  ...  0*53  „ 

D'Allest          „ 0-539  „ 

Niclausse        „     ...  ...  ...  ...  0-466  „ 

Du  Temple    „    (old  type)...  ...  ...  0-329  „ 

„  „    (present)  ...  ...  ...  0-411  „ 

Normand         „    (present)  ...  ...  ...  0*421  „ 

Thornycroft    ,,    (old  type)  ...  ...  0*356  ,, 

„  „    ("Speedy"  type)    ...  ...  0-453  » 

These  are  the  weights  for  boilers  of  warships  only.  The 
weights  of  cylindrical  boilers  for  two  transatlantic  liners  amount 
to  1*27  tons  per  square  foot  of  grate. 

M.  Bertin  remarks  : — 

"The  weight  per  square  foot  of  grate  surface  of  modern  tubulous  boilers 
considered  suitable  for  use  on  large  ships  is  very  nearly  half  that  of  the 
ordinary  return-tube  cylindrical  boilers.  The  weight  of  the  lightest  class  of 
tubulous  boilers  is  about  one-third  those  of  Admiralty  cylindrical  type,  that  is 
to  say,  nearly  equal  <o  the  weight  of  water  contained  in  these  latter. 

"  The  weight  per  square  foot  of  grate  would  represent  the  relative  weights 
of  different  boilers  if  the  evaporative  power  per  square  foot  of  grate  were  the 
same  for  all.  This  is  very  far  from  being  the  case,  especially  in  the  Navy, 
where  forced  draught  is  almost  universally  used,  The  relative  weights  of 


THE  MODERN  STEAM  BOILER.  589 

boilers  can  thus  only  be  determined  after  very  careful  examination,  which  in 
the  nature  of  the  case  must  be  incomplete,  as  it  is  impossible  to  determine 
with  any  exactness  the  maximum  evaporative  power  of  a  boiler. 

Weights  of  Water. — "The  Admiralty  type  of  cylindrical  boiler  contains 
IQ'66  cubic  feet  of  water  per  square  foot  of  grate,  and  the  return-tube  or 
Scotch  boiler  7-38  cubic  feet,  giving  a  mean  of  9-02  cubic  feet  for  cylindrical 
boilers.  In  locomotive  boilers  the  mean  is  as  low  as  4-92  cubic  feet,  varying 
between  4-26  and  5*58." 

Amongst  tubulous  boilers  the  Belleville  has  0*855  cubic  feet, 
the  Niclausse  2*07,  and  the  D'Allest  type  2*69  cubic  feet.  Similar 
figures  have  been  published  from  time  to  time  for  numerous 
water-tube  boilers  arranged  for  use  on  land,  but  those  just 
quoted  may  be  taken  as  typical  examples  of  marine  boilers. 

Cost  and  Durability. — The  only  authentic  figures  of  cost  of 
water-tube  boilers,  as  compared  with  cylindrical  boilers,  which 
have  as  yet  been  published,  are  those  given  by  M.  Bertin  in  his 
book.  Writing  in  1898,  M.  Bertin  said  : — 

"  The  price  per  square  foot  of  grate  of  the  Belleville  Boilers  bought  by  the 
French  Navy  during  the  last  few  years,  has  varied  between  £27-12  and 
£35'62  ;  on  an  average  £3i'96.  The  Niclausse  boilers  of  the  "  Friant  "  have 
also  cost  £3i'96.  For  the  D'Allest  boilers  the  price  is  a  little  higher  ;  it  has 
ranged  from  £27' 12  to  £38-64  ;  on  an  average  £33*45. 

"Comparing  the  average  price  of  cylindrical  boilers  with  the  foregoing,  we 
find  it  to  be  £327  for  single  or  double-ended  return-tube  boilers,  £48-31  for 
direct  tube  or  Admiralty  boilers,  and  £5276  for  boilers  of  the  locomotive 
type.  ...  In  reckoning  the  performance  per  square  foot  of  grate, 
tubulous  boilers  are  25  per  cent,  dearer  than  the  return-tube  boilers,  but  they 
are  10  per  cent,  cheaper  than  Admiralty  boilers,  which  have  in  some  cases 
supplanted  the  return-tube  boilers. 

"  There  is  only  one  example  of  tubulous  boilers  of  the  second  group  being 
bought  for  ships  other  than  small  craft  ;  that  is,  the  Normand  boilers  of  the 
'  Dunois'  and  of  the  'Lahire,'  costing  £64-65  per  square  foot  of  grate.  This 
price  hardly  affords  a  fair  comparison,  as  there  is  no  analogous  case  in  the 
other  series  of  boilers  excepting  the  cylindrical  boilers  of  the  '  Fleurus,1 
which  cost  £65-39.  The  Guyot  boilers  of  the  '  Jeanne  d'Arc,'  according  to 
the  highest  estimate  will  only  cost  £44'59  ;  this  price  is  still  high,  but  it 
falls  below  that  of  the  Admiralty  type  boilers,  and  moreover  it  is  unfair  to  the 
Normand  and  Guyot  boilers  to  assume  that  the  same  amount  of  power  per 
square  foot  of  grate  surface  could  be  obtained  from  boilers  of  the  Admiralty 
type  as  from  them." 

On  the  question  of  durability  of  water-tube  boilers,  there  is 
more  information  available  than  is  commonly  supposed.  An 
article  in  Engineering  of  the  27th  December,  1867,  from  the  pen 
of  the  late  Mr.  Ferdinand  Kohn,  and  a  letter  in  the  same  journal 


59o  THE  PRACTICAL  PHYSICS  OF 

of  23rd  October,  1874,  by  the  author  of  this  work,  contain  the 
evidence  that  several  examples  of  Rowan  and  Horton  marine 
boilers  continued  in  active  service  at  a  pressure  of  120  Ibs.  per 
square  inch  for  close  on  ten  years,  almost  without  repair, 
although  subject  to  annual  Board  of  Trade  survey.  At  that  time 
few  cylindrical  marine  boilers  were  able  to  continue  working  at 
their  original  pressure  of  50  to  60  Ibs.  for  more  than  three  years. 
In  his  paper  on  "Water-Tube  or  Coil  Boilers,"  read  at  the 
Engineering  Congress  in  Chicago  in  1894,  Mr.  C.  Ward 
mentioned  that  one  of  his  boilers,  having  700  sq.  ft.  of  heating 
surface  and  32  sq.  ft.  of  grate  area,  had  worked  at  180  Ibs.  steam 
pressure  for  fourteen  years,  requiring  the  renewal  of  only  two 
tubes  during  that  time.  Mr.  Roberts  also,  in  the  discussion  on 
that  paper,  stated  that  one  of  his  boilers  had  been  in  use  for 
thirteen  years,  during  the  summer  seasons,  and  that  it  had 
received  no  repairs.  Other  makers  had  similar  experience  even 
then,  and  in  fact  the  general  result  of  American  experience  has 
been  summed  up  by  Professor  R.  H .  Thurston  in  his  contribution 
to  the  discussion  on  the  author's  paper  "  On  Water-Tube  Boilers  " 
in  1897.  "  Durability,"  he  said,  "was  a  marked  feature  of  this 
class  of  boilers  with  them  (i.e.,  the  Americans),  and  the  cost  per 
horse-power  hour  or  year  was  remarkably  small,  as  reckoned  on 
the  repair  and  maintenance  account.  Their  most  extensive 
builders,  after  obtaining  the  statistics  of  between  100,000  and 
200,000  h-p  of  their  boilers  in  use,  and  from  one  to  above  twenty 
years'  service,  reported  these  costs,  as  an  average,  to  fall  under 
five  cents  per  horse-power  year.  As  to  economy,  they  found 
records  of  trials  in  which  an  aggregate  of  above  3,000  tons  of 
water  was  evaporated  by  270  tons  of  fuel,  an  average  efficiency 
which  he  thought  the  older  types  of  boiler  did  not  attain  ;  it  was 
within  ten,  perhaps  seven,  per  cent  of  unity  efficiency.  During 
an  experience  in  professional  work  of  now  35  years,  and  dating 
from  the  earliest  days  of  commercial  use  of  this  class  of  boiler, 
he  had  never  known  of  their  causing  loss  of  life  or  of  property 
by  explosion.  The  comparatively  few  minor  accidents  recorded 
had  been  due  to  isolated  cases  of  incomplete  utilization  of  the 
fundamental  principles  of  construction,  or  to  exceptional  mis- 
management. If  properly  built  and  maintained  in  good  order 
by  regular  and  wise  repair,  they  practically  never  wore  out,  and 
never  endangered  life  or  property.  They  bore  hard  driving, 


THE  MODERN  STEAM  BOILER.  591 

and  to  an  extraordinary  amount  ;  he  thought  their  record  was 
to-day  vastly  higher  in  this  respect  than  any  shell  boilers.  They 
enormously  economised  weight  and  space,  and  had  always 
seemed  to  him  certain,  in  time,  to  displace  the  older  types,  even 
at  sea,  where,  indeed,  they  were  particularly  needed.  Their 
latest  experience  with  them  lent  additional  confidence  to  their 
ultimate  adaptation  to  even  this  trying  duty,  and  if  steam  pres- 
sure continued  to  rise  50  per  cent,  per  decade,  it  could  not  be 
long  before  they  would  entirely  supplant  the  shell  boiler  in  all 
naval  and  long  voyage  craft,  and  probably  in  all  sea-going  ships. 
The  report  of  the  Engineer-in-Chief  of  the  United  States  Navy, 
just  issued,  dated  October  ist,  1897,  includes  the  following 
statement  relative  to  the  introduction  of  water-tube  boilers  into 
the  batteries  of  boilers  on  naval  vessels,  a  movement  of  supreme 
importance,  and  one  which  had,  as  already  noted,  been  going  on 
for  a  long  time  in  that  service  : — :'  The  gradual  replacement  on 
war  vessels  of  the  familiar  cylindrical  boiler  by  various  forms  of 
the  water-tube  boiler  constitutes  the  most  important  fact  in 
marine  engineering  at  this  time.  For  torpedo  boats  their 
superiority  was  so  evident  that  they  quickly  displaced  the  older 
type  and  have  been  used  exclusively  for  some  years,  although 
their  first  appearance  (on  the  "  Ariete  ")  was  only  ten  years  ago. 
The  particular  form  used  in  torpedo  boats  is,  however,  of  such 
light  scantling  that  hitherto  there  has  been  a  fear  that  its 
longevity  would  not  be  sufficient  to  warrant  the  use  of  such 
boilers  in  large  vessels.  A  different  form  has  been  in  use  in  the 
French  Navy  since  1879,  a°d  has  also  been  used  in  other  navies, 
in  some  very  extensively,  but  the  saving  of  weight  due  to  its 
use  has  not  been  so  great  as  seems  desirable  if  the  cylindrical 
boiler  is  to  be  definitely  abandoned.  In  1888,  this  Bureau,  alive 
to  the  supreme  importance  of  light  machinery  for  naval  vessels, 
advised  the  Department  to  invite  a  competition  of  manufacturers 
of  water-tube  boilers  with  a  view  to  the  adoption  of  the  success- 
ful one  for  use  in  a  naval  vessel.  As  a  result  of  this  action,  coil 
boilers  were  installed  in  the  "  Monterey"  in  1892,  and  have  been  in 
successful  use  ever  since.  This  was  the  first  instance  of  the  use 
of  light  water-tube  boilers  for  a  large  power  (over  4,000  I.H.P.) 
on  a  large  ship.  It  would  have  been  easy  for  this  Bureau  to 
gain  a  cheap  reputation  for  progressiveness  by  adopting  this 
type  of  boiler  at  once  for  all  ships,  but  there  had  not  been  sum- 


592  THE  PRACTICAL  PHYSICS  OF 

cient  experience  in  the  use  of  these  boilers  for  extended  cruising 
at  sea  to  make  such  a  step  judicious,  and  for  the  highest  efficiency 
of  the  fleet.  The  Monterey  was  expressly  designed  for  coast 
defence,  so  that  she  would  always  be  near  repair  shops  if  neces- 
sary, and  her  case  was  different  from  that  of  ships  designed  for 
general  cruising.  The  conditions  of  the  building  of  our  new 
Navy  made  it  imperative  that  every  unit  should  be  absolutely 
reliable.  We  were  not  adding  to  a  navy  up-to-date,  but  were 
replacing  obsolete  ships  with  modern  ones.  With  only  three 
battleships  in  commission,  we  could  not  experiment  on  the  few 
additional  ones  authorised.  Consequently,  although  realising 
the  advantages  of  a  reduction  of  boiler  weights,  if  obtained 
without  sacrificing  reliability,  the  Bureau  has  used  cylindrical 
boilers  in  the  recent  battleships.  Meanwhile,  experience  of  our 
own  has  been  acquired  from  the  service  of  the  "  Monterey/'  the 
"Gushing,"  and  the  "  Ericsson,"  and  careful  attention  has  been  paid 
to  what  is  doing  in  the  merchant  marine  and  in  foreign  naval 
services.  The  last  report  of  the  Bureau  showed  the  adoption  of 
Babcock  and  Wilcox  boilers  for  the  "  Chicago"  and  for  the  "  Anna- 
polis" and  the  "  Marietta."  Since  then  it  has  been  decided,  in  the 
modernising  of  the  "  Atlanta's  "  machinery,  to  use  this  same  make 
of  boiler  for  about  two-thirds  of  her  power.  The  "  Nashville  "  has 
Yarrow  boilers  for  about  the  same  fraction  of  power.  As  is 
shown  elsewhere  in  this  report,  the  "  Annapolis,"  "  Marietta,"  and 
"  Nashville  "  have  passed  their  contract  trials  successfully,  and  their 
water-tube  boilers  were  entirely  satisfactory.  The  Bureau  feels 
that,  with  the  experience  now  gained,  the  efficiency  of  the  fleet 
will  be  best  served  by  using  water-tube  boilers  on  future  ships. 
As  yet,  it  can  certainly  not  be  said  that  any  one  of  the  numerous 
varieties  of  water-tube  boilers  is  absolutely  the  best.  Some  of 
the  ablest  engineers  in  the  world  have  identified  their  names 
with  particular  forms  of  this  type  of  boiler,  and  it  is  probable 
that,  as  t  xperience  accumulates,  a  form  of  boiler  will  be  evolved 
embracing  the  best  features  of  all  of  them.'  ' 

In  a  paper  on  "  W7ater-tube  Boilers  in  the  U.  S.  Navy,"  read 
in  November,  1899,  to  the  Society  of  Naval  Architects  and 
Marine  Engineers  in  New  York,1  Admiral  G.  WT.  Melville,  the 
Engineer-in-Chief  of  that  Navy,  said  that  the  decision  to  adopt 

1  Abstract  published  in  The  Mechanical  Engineer,  December  16,  1899  ;  see 
Science  Abstracts,  Vol.  iii.,  p.  102. 


THE  MODERN  STEAM  BOILER.  593 

water-tube  boilers  in  all  future  vessels  of  their  Navy  was  a 
natural  step  in  the  advance  towards  a  perfect  righting  machine. 
This  opinion  is  all  the  more  remarkable  that  in  the  same  paper 
he  announced  that  as  an  engineer  he  considers  the  design  of 
these  boilers  to  be  wrong  in  principle,  but  he  has  become  con- 
vinced that  in  spite  of  all  drawbacks  they  are  tactical  necessities 
for  warships.  The  grounds  upon  which  he  Objects  to  their 
design  are,  that  the  pressure  is  borne  on  the  inside,  instead  of 
on  the  outside,  of  the  tubes,  this  being,  he  considers,  the 
weakest  part  of  the  boilers  ;  that  there  is  a  smaller  quantity  of 
water  carried  in  these  boilers  than  in  the  cylindrical  type  ;  that 
there  is  difficulty  in  observing  the  leaks  in  the  tubes  ;  and  that 
the  value  of  the  heating  surface  is  less  than  in  the  other  design. 
There  seems  to  be  less  force  in  the  first  objection  than  in  the 
others,  because  in  order  to  have  a  pressure  of  steam,  some  sort 
of  vessel  must  be  supposed,  and  the  only  question  is  as  to  the 
best  form.  The  circular  is  the  strongest  form  for  resisting 
pressure,  and  the  smaller  the  diameter  the  greater  the  strength 
per  unit  of  surface.  Tubes  as  made  may  be  weaker  under 
pressure  from  within  than  under  conditions  which  expose  them 
to  a  collapsing  pressure,  but  that  is  a  question  of  material  and 
thickness,  not  of  form.  Moreover,  in  order  to  have  any  con- 
siderable amount  of  heating  surface  obtained  from  fire-tubes,  a 
vessel  of  considerable  size  is  required,  as  in  the  cylindrical 
boiler,  with  all  its  attendant  drawbacks,  in  view  of  the  higher 
pressure  of  steam.  As  to  the  other  grounds  of  objection,  the 
smaller  quantity  of  water  necessitates  greater  perfection  in  the 
feed  arrangements,  and  more  careful  attention,  which  are  by  no 
means  insuperable  difficulties  ;  and  the  heating  surface  question 
is  in  a  fair  way  of  being  settled.  "  At  first,"  says  Admiral 
Melville,  "  the  heating  surface  of  water-tube  boilers  was  made 
3  sq.  ft.  per  H.P.,  as  against  2  sq.  ft.  necessary  with  cylindrical 
boilers.  This  figure  has  been  gradually  reduced,  until  now  we 
are  down  to  2*4  sq.  ft.  of  heating  surface  per  H.P.,  about  as  low 
as  I  think  it  is  yet  safe  to  go  with  water-tube  boilers.  .  .  The 
ratio  of  heating  to  grate  surface  has  been  kept  up  to  at  least  40, 
although  we  do  not  yet  feel  warranted  in  allowing  as  small  grate 
surface  in  water-tube  as  in  cylindrical  boilers.  Water-tube 
boilers  lose  in  efficiency  when  forced,  especially  those  of  the 
straight  tube  type.  .  .  .  The  increased  grate  surface  we  have 


594  THE  PRACTICAL  PHYSICS  OF 

acquired  with  water-tube  boilers  will  be  a  positive  advantage  to 
our  ships'  steaming  qualities.  I  consider  that  sustained  sea 
speed  depends  largely  upon  the  grate  surface." 

Since  the  "  Gushing,"  all  torpedo  boats  and  destroyers  in  the 
American  Navy  have  been  equipped  with  water-tube  boilers, 
which  have  proved  to  be  quite  as  reliable  as  the  light  engines 
used  in  these  vessels,  and  by  making  the  attainment  of  higher 
speeds  possible,  have  added  to  their  efficiency  and  security. 

The  water-tube  boilers  in  the  "  Monterey  "  (Ward  boilers), 
the  "  Nashville  "  (Yarrow  boilers),  the  "  Marietta  "  (Babcock- 
Wilcox  boilers),  the  "  Annapolis "  (Babcock-Wilcox  boilers), 
and  the  "  Chicago  "  (Babcock-Wilcox  boilers),  have  come  suc- 
cessfully through  a  considerable  amount  of  service.  The 
"  Monterey  "  made  a  voyage  of  about  8,000  knots,  largely  under 
forced  combustion,  and,  whenever  possible,  with  all  boilers  in 
use.  "  There  was  no  resultant  injury  to  the  water-tube  boilers, 
which  performed  well  throughout  the  trial,  but  the  combustion 
chambers  of  the  cylindrical  boilers  came  out  of  the  trial  badly 
bulged."  The  "  Marietta"  made  a  trip  around  South  America  at 
the  beginning  of  the  war  with  Spain,  and  no  repairs  were  required 
to  the  boilers  after  the  completion  of  the  trip.  The  "  Annapolis  " 
and  "Chicago"  also  maintained  the  same  level  of  excellence. 

The  boilers  of  the  "  Monterey  "  have  been  twice  re-tubed  on 
board  the  ship  by  the  engineering  staff  there,  without  the 
necessity  of  laying  up  the  ship  at  a  Navy  Yard,  and  in  the  case 
of  the  old  monitors,  "  Canonicus,"  "  Mahopac,"  and  "  Man- 
hattan," the  old  rectangular  boilers,  which  were  worn  out,  were 
replaced  *by  Babcock-Wilcox  land-type  boilers  without  dis- 
turbing the  vessels'  decks.  The  old  boilers  were  cut  up  and 
passed  out  through  the  funnel,  down  which  parts  of  the  new 
boilers  were  passed.  They  were  assembled  in  the  engineroom  space 
and  erected  in  position,  the  whole  operation  having  taken  less  time 
than  was  required  for  the  construction  of  the  original  boilers. 

In  the  case  of  vessels  having  protective  decks,  the  facility 
with  which  water-tube  boilers  can  be  removed  or  completely 
renewed  without  disturbing  the  elects  is  of  immense  im- 
portance, and,  with  the  result  named  above,  is  impossible  with 
cylindrical  boilers.  The  following  vessels  are  being  fitted  wholly 
or  partially  with  water-tube  boilers  :— The  "  Alert,"  "'Atlanta," 
"Cincinnati,"  and  "Wyoming,"  with  Babcock-Wilcox  boilers; 


THE  MODERN  STEAM  BOILER.  595 

the  "  Maine  "  and  "  Connecticut,"  with  Niclausse  boilers  ;  the 
"  Missouri,"  "  Wisconsin,"  and  "  Arkansas,"  with  Thornycroft 
boilers  ;  and  the  "  Florida  "  with  modified  Normand  boilers. 

No  trouble  has  as  yet  been  experienced  from  salt  water  or 
grease  in  water-tube  boilers,  but  in  the  short  war  with  Spain 
several  of  the  U.S.  vessels  suffered  severely  from  dropped 
furnaces  in  their  cylindrical  boilers. 

With  regard  to  the  accidents  and  failures  reported  against 
water-tube  boilers,  Admiral  Melville  says  that  we  hear  of  all  the 
failures,  but  the  successes  are  not  mentioned.  He  considers  that 
the  experience  of  the  last  ten  years  or  more  in  the  U.S.  and 
other  navies  proves  that  water-tube  boilers,  when  proper  pre- 
cautions are  used,  can  be  successfully  adopted  for  the  steam- 
generating  plant  of  ocean-going  vessels. 

In  the  French  Navy,  according  to  M.  Berlin,  the  Belleville 
boilers  are  the  only  type  of  tubulous  boilers  which  have  been  in 
service  for  any  length  of  time.  "  The  ease  with  which  the 
various  elements  can  be  replaced  renders  it  very  difficult  to 
determine  exactly  the  real  life  of  the  boiler  ;  the  replacing  of 
the  ash-pans  and  casings,  which  in  itself  is  a  small  matter,  is  to 
some  extent  a  guide  in  this  direction.  The  Belleville  boilers  of 
the  '  Milan '  in  1891,  had,  in  the  course  of  a  few  months, 
several  tubes  pitted  through  sufficiently  to  put  the  boat  out  of 
service,  although  they  were  in  good  condition  when  she  started, 
while  on  the  '  Voltigeur/  the  Belleville  boilers,  which  have  been 
renewed  piecemeal  during  almost  twenty  years,  have  always 
behaved  well,  and  successfully  withstood  the  test  of  several  long 
commissions. 

11  Just  as  unfavourable  examples  can  be  quoted  for  cylindrical 
boilers  as  for  tubulous,  as  is  evidenced  in  the  case  of  the 
'  Marceau '  during  her  Cronstadt  commission,  where  the  same 
thing  happened  as  on. board  the  l  Milan.'  We  may,  therefore, 
arrive  at  the  conclusion  that  the  use  of  cylindrical  boilers  does 
not  offer  a  guarantee  of  continuous  satisfactory  working  much 
superior  to  that  of  the  Belleville  boilers.  Further,  exact  com- 
parison will  never  be  possible  between  two  durabilities  of  which 
one  only  can  be  defined.  The  cylindrical  boilers  of  warships 
have  a  life  of  eight  years,  or  at  most  ten,  including  at  least  one 
thorough  overhauling  during  that  period.  They  are  then  con- 
demned and  broken  up,  although  still  containing  a  good  many 


596  THE  PRACTICAL  PHYSICS  OF 

sound  portions,  because  there  is  of  necessity  a  limit  to  patching. 
At  the  end  of  ten  years  a  tubulous  boiler  will  not  have  experi- 
enced a  thorough  overhaul,  but  will  have  undergone  a 
good  many  repairs  ;  some  parts  may  have  been  already 
changed  twice,  and  even  need  replacing  a  third  time,  without  in 
any  way  prejudicing  those  portions  of  the  boiler  which  have 
remained  intact  ;  there  is  then  no  reason  why  the  boiler  should 
be  condemned. 

"  The  foregoing  considerations  appear  favourable  to  tubulous 
boilers  in  regard  to  durability,  but  it  would  be  unwise  to 
generalise.  Tubular  boilers,  in  certain  conditions  of  work  and 
maintenance,  have  a  very  long  life  without  necessitating  any 
very  extensive  repairs."  Instance  the  case  of  the  White  Star 
Company,  where  the  boilers  worked  for  twenty-four  years, 
and  that  of  the  "  Notre  Dame  du  Salut,"  whose  boilers  had 
undergone  twenty  years  of  service  up  to  the  time  when  the 
vessel  was  chartered  by  the  French  Navy.  "  A  tubulous  boiler 
would  not,  in  all  probability,  have  reached  this  advanced  age 
without  having  often  had  different  parts  replaced  by  new  ones.  .  .  . 
On  the  other  hand,  when  the  conditions  are  altogether  against 
durability,  as  on  torpedo  boats,  where  locomotive  boilers  only  last 
three  years,  tubulous  boilers  offer  a  decided  advantage. 

"  Mr.  Thornycroft  states  that  his  boilers  usually  stand  eight 
years'  service  without  extensive  repairs,  certainly  without  a 
thorough  overhauling." 

Although  these  remarks  seem  at  present  to  put  the  case  fairly, 
it  must  not  be  forgotten  that  a  longer  experience  of  tubulous 
boilers  may  materially  change  that  aspect  of  this  question.  The 
proportion  of  tubulous  to  cylindrical  boilers  in  actual  use  at  sea 
is  as  yet  small,  and  "it  is  unreasonable  to  suppose  that,  as  ex- 
perience accumulates,  water-tube  boilers  will  not  be  as  durable 
as  any  others  in  proportion  to  the  work  done  by  them."  l 

Moreover,  as  Mr.  Milton  has  remarked,2  "  it  must  be  remem- 
bered that  treatment  is  the  most  vital  factor  in  the  question,  and 
that  the  present  long  service  obtained  from  ordinary  boilers 
has  only  been  realised  as  the  result  of  long  years  of  experience 

1  "  On  Water-Tube  Boilers,"  by  F.  J.  Rowan.     Trans.  Inst.  Eng.  and  Ship- 
builders in  Scotland      Vol.  xli.,  p.  35. 

2  "  Water-tube  Boilers  for  Marine  Engines,"  by  J.  T.  Milton.     Min.  Proc. 
Inst,  C,E.     Vol.  cxxxvii.,  p.  301, 


THE  MODERN  STEAM  BOILER. 


597 


as  to  the  best  methods  of  management.  There  was  a  time 
when  a  life  of  eight  years  was  looked  upon  as  an  excellent 
result,  whereas  now  20  years'  service  is  by  no  means  un- 
common, and  is  often  exceeded.  If  wrater-tube  boilers  become 
common,  experience  will  doubtless  soon  show  the  best  means 
of  preserving  them/' 

Hudson's  Tables.— The  following  tables  by  Mr.  J.  G.  Hudson, 
referred  to  in  Chapter  IV.,  show  some  of  the  results  of  trials 
already  quoted  herein,  calculated  out  to  show  the  disposal  of  the 
heat  of  the  fuel  and  the  velocity  of  the  fire  gases. 


TABLE  CXVIII. 

Fire-tpx  Evaporation,  by  formulas  (1),  (2),  and  (8), 
for  various  ratios  of  surf  act  and  air  supply,  assuming  air  at 
60  dcff.,  steam  at  340  dcg.,  and  14,000  unit*  developed  per  1  ll>. 
qfcoaL 


F=H.8. 
per  1  Ib. 
fuel. 

A  =  air  per  lib.  fuel   ..     .. 
tp  =  heat  capacity  of  gases 
Ha  =  heat  unite  available     .  . 

121b. 
3-12 
18,126 

18  Ib. 
4-56 
12,728 

24  Ib. 
*6'0 
12,820 

sorb. 

7-44 
11,917 

sq.ft. 

•03 

Absorbed  per  so  .  f  t.     .  . 
Temperature  of  the  gasea  .. 

44,533 
1,336 
4,119' 

29,600 
888 
2,935° 

21,910 
657 
2,284° 

17,100 
613 
1,878° 

•1 

it           u           it         •• 
it           it           »i         •• 
ii           ii           it          •  • 

85,670 
3,567 
8,404° 

25,450 
2,545 
2,572° 

19,460 
1,946 
2,069° 

16,540 
1,654 
1,733° 

•3 

»i           it           ti          •  • 
•»           it          ii          •  • 
u           ii           ii 

23,163 
6,949 
2,820° 

18,177 
5,458 
1,984° 

14,788 
4,486 
1,664° 

12,827 
8,698 
1,445* 

%5 

ti           ••           M          •  • 

fl                   H                   »»                •• 
II                   II                   II* 

17,120 
8,560 
1,803° 

14,138 
7,069 
1,580° 

11,924 
5,962 
1,400° 

10,216 
5,108 
1,256° 

•7 

It                   II                   II                 •'• 
l»                   II                  II 

n            ti            ti           •  • 

13,579 
9,505 
1,500° 

11,666 
8,096 
1,856° 

9,990 
6.993 
1,228° 

8,704 
6,094 
1,121° 

1-0 

H             »r            it 
ii             ii             >i           •  • 

t»                     II                      II                   •• 

10,363 
10,363 
1,225° 

9,088 
9,088 
1,137° 

8,035 
8,036 
1,064° 

7,150 
7,160 
981° 

15 

II                 II                 II               •  • 

It                 *t                 II               •• 
tl                 tt                l» 

7,430 
11,145 
075° 

6,697 
10.045 
927° 

6,059 
9,089 
878° 

6,600 
8,250 
883° 

2-0 

tt                 t»                 tl               •• 
It                 It                 II 
1*                 1*                 tl 

6,791 
11,582 
835° 

5,301 
10,603 
805° 

4,863 
9,726 
772° 

4,460 
8,938 
740- 

3-0 

II                    tl                    M                  •• 
II                    II  •                  It                 •  • 
•1                    It                    tl                  •• 

4,0  8 
12,054 
683° 

3,742 
11,220 
608° 

3,486 
10,460 
650° 

3,251 
9,752 
681° 

40 

It                    il                    tl 
II                    tl                    It                  •• 
It                    II                    II 

3.0T9 
12,316 
600° 

2,891 
11,503 
694° 

2,717 
10,870 
682° 

2.6M 
10,216 
669° 

598 


THE  PRACTICAL  PHYSICS  OF 


TABLE 


Source  of  data. 

Per  lib.  of  coal  fired. 

Heat  absorbed 
per  sq.  ft.  of 
firebox. 

Entering  the  tubes. 

Heating  surface. 

i|l 

|* 

3s 

Heat 
deve- 
loped. 

ii 

ii 

IVansr 

Per 

deg. 

nissiou. 

Per 
sq.  ft 

ii 

Tubes 

Potal. 

a 

sq.  ft 

sq.  ft. 

q.  ft. 

lb. 

units 

units 

•ah 

SB 

ft 

units 

units 

Report  of  the      ( 

Fusl  Yama     .  . 

5 

T79 

2-29 

0157 

22-3 

12,500 

11,036 

288 

17-C3 

4-2 

4,120 

Research  Cora-     I 
mittee,          1 

Colchester      ..     .. 

15 

•80 

1-01 

008 

18-5 

13,054 

21,053 

IM 

42-2 

8-82 

16,237 

last  Mech.  Bng.   \ 

Tartar      ..     ...    .. 

4 

2-825 

2-726 

022 

81-6 

14,700 

11,200 

s'ro 

18-8 

4-64 

4,57(5 

Mr.  Spencc's  trials  f 
of  a  low         \ 
Navy-type  boiler.*  1 

Natural  draught  .. 
Cold  forced  do.      .  . 
Hot  (201*)  forced  do. 

28 
24 
SI 

1-34 
1-08 
l-4« 

1-62 
1-82 
1-77 

0109 
009 
012 

16'6 
20-0 
18-0 

18,000? 

18,458 
17,216 
17,967 

n« 

833 
879 

25-2 
85-8 
24-3 

6-8 
7-26 
6-12 

10.1C2 
11,108 
9,645 

1" 

D  Natural  draught 

4 

8'6 

9-0 

054 

17-4 

14,045 

17,000 

885 

5'25 

2-92 

4,305 

A        ,i           i, 

24 

6-26 

5-6 

083 

24' 

12,600? 

18,796 

OCR 

10-45 

8-76 

4,610 

0  -27in.          „ 

143 

8-187 

8-23 

02 

17-8? 

14,500? 

24,294 

500 

18-8 

6'5 

13,812 

B  -49in.          „ 

09 

1-M 

2-05 

01X8 

18-14 

14,270 

26,089 

051 

81-8 

8-88 

20,299 

. 

B  2  OWn. 

046 

i-fM 

105 

000 

17  2 

13,622 

28,543 

878 

60-4 

3'6 

83,973 

{" 

Draught  Sin  

oc 

•01 

•87 

00318 

20'  t 

13,900? 

24,683 

524 

82-5 

7-4 

87,862 

,,         Bin  

•05 

•477 

•527 

00246 

18-  T 

13,850  ? 

26,760 

W 

60 

'0 

46,920 

„        4in...     .. 

•04 

•88 

•42 

0011)7 

!«•? 

12,750  ? 

29,276 

MM 

89-4 

22-8 

58,163 

, 

61n  

•031 

•809 

•84 

00160 

14'  ? 

12,860  ? 

83,007 

MM 

226' 

26-9 

76,907 

Alnwick  

•4 

1-105 

1-505 

0084 

28-2 

18,264 

12,820 

4CO 

36-9 

6-67 

7,470 

Foden  (simple)     .. 

•68 

6-12 

6-8 

•08 

12-42 

18,964 

13,628 

519 

6-68 

2-06 

8,104 

„      (compound) 

•56 

6-09 

6-65 

•028 

16-22 

14,715 

14,877 

607 

8-16 

8-46 

4,460 

aA.S.E.  portable 

McLaren  (a.)  ..     .. 

•8 

4-1 

4-9 

•0144 

26-2 

14,940 

9,427 

1194 

20-8 

4-61 

8,832 

engine  trial* 

„       (c.)   ..     .. 

•744 

4-026 

4-77 

•014 

27-48 

14,880 

9,458 

1213 

22-7 

4-77 

4,031 

at  the 
Newcastle  Show, 

D.,  P.,  and  Co.  (..) 

•G3 

4'M 

5-41 

•022 

23'5 

14,646 

9,267 

11C4 

12' 

8-87 

2,773 

1887. 

(c.).. 

•75 

5-29 

6-04 

•0255 

24-43 

14,664 

9,899 

1247 

11-4 

8-42 

8,013 

Humphreys  (s.)    .. 

•82 

I'M 

1-88 

•0116 

17'4 

14,788 

19,187 

•>014 

25-8 

6-63 

11,178 

(c.)    .. 

•20" 

1-208 

1*44 

•0089 

23-67 

14,076 

16,840 

1789 

41-4 

7-85 

11,890 

Cooper     

•35 

1-62 

1-97 

•01 

19' 

14,544 

17,014 

1S49 

30-6 

6-9 

10,307 

Gladstone       ..     .. 

•092 

1-108 

1-2 

•0028 

18'  ? 

14,500? 

26,717 

2701 

141- 

18-9 

44,290 

Mr.  Blroudley.*  \ 

•22 

2-64 

2-76 

•0068 

,, 

„ 

21,282 

mi 

49-1 

9-8 

18,191 

Mr.  HollldayS  .  .     . 

Lancashire  boiler.. 

•s 

8-40 

8-76 

•058 

18-18 

14,568 

23,190 

2299 

4-86 

2-94 

5,880 

Donkin  &  Kennedy 

Do.  (same  boiler)  .. 

•Ml 

1-927 

2-09 

•082 

17-00 

14,589 

24,801 

2473 

10-8 

4-94 

10,710 

Mr.  Longridge?    ] 

Lancashire  boiler.. 
Do.  (same)     ..     .. 

•11 
•13 

1-412 
1-588 

1-58 
1-72 

•0148 
•0156 

20-7 
14-8 

12,665 
12,522 

19,483 
24,977 

205. 
MM 

24'4 

18-4 

6-53 
0-4 

11,271 

18,863 

Worthington    pumj 
trialss    

Cornlah  boilers      .. 

•20 

4-97 

6-26 

•084 

16-42 

14,800 

20,88(0 

214 

3-CS 

2-C3 

4,042 

University  College 

"4  Loco,  type    ..     / 

•87 

2:09 

2-46 

•0204 

27-2 

13,900 

13,160 

133 

17-1 

4-17 

4,899 

Donkin  &  Kennedy 

/Do.  (same)..     \ 

•67 

8-76 

4-48 

•037 

40-7 

14,316 

7,687 

100 

11-20 

8-01 

2.0T- 

THE  MODERN  STEAM  BOILER. 


599 


CXIX. 


Leaving  the  tubes. 

o  jj                           Disposal  of  the  beat  developed  by  1  Ib.  of  the  fuel 

Jj 

Is 

Temp,  of  i 
the 
gases. 

I 

Apparent  absorption 
by 

Apparent  total 
absorption. 

Wasted  in  gasoa. 

Actually, 
utilised  in 
raising 
steam. 

Firebox. 

Tubes. 

Calculated. 

Actual. 

Calcu- 
lated. 

Actual. 

Cal. 

Act, 

ft. 

n  'H 

U 

••a)) 

-'ah 

units     % 

unita     % 

units       % 

units        % 

unitB     % 

units     % 

unita       % 

10-87 

•43 

uf 

>78' 

304 

6518  44-2 

8819  30-6 

9,387  74-7 

9,547  70  4 

8103  25-3 

2953  23-0 

8,570  68  0 

20-96 

•83 

845 

S35 

324 

3158  24-8 

6218  47-0 

9,376  71-9 

9,427   72-2 

3074  28  1 

3627   27-8 

8,240  C3 

11-4 

•oo 

'.80 

477 

362 

4480  80-4 

5384  36-8 

9,804  07-2 

11,447  77-9 

4830  32-8 

3253  22-1 

T         T 

11  9 

•o 

000 

757 

303 

6167  89-7 

6301   40-8 

10,408  80-6 

10,059  77-4 

2532  19-5 

2941   22-0 

9,293  71  6 

18-6 

•47 

745 

834 

,, 

4132  31-7 

5416  41  7 

9,548  73-4 

9,099  70  0 

3452  2<J-0 

3901   30-0 

8,981  09  1 

11-7 

•58 

600 

701 

„ 

5570  42-8 

5611   43-2 

11,181   86-0 

10,994  84-0 

1819  14  0 

2006  15'4 

10,875  79-8 

1-98 

•97 

124 

421 

880 

6880  40-0 

6456  43-2 

13,336  89-2 

13,330.  89-2 

1009   10-8 

1616  10-8 

12,944  80  7 

4-78 

•50 

485 

474 

382 

8811  20-2 

6739  53-6 

10,050  79-8 

10,116  80-3 

2550  20-2 

2484  19-7 

T         T 

6-15 

•82 

535 

640 

375 

3474  24-0 

8884  61'2 

12,358  85-2 

12,834  85-1 

2142  14-8 

2106  14  ft 

12,056  83  0 

10-91 

•5 

605 

610 

365 

2848  16-6 

9415  65-9 

11,763  82-4 

11,740  82-3 

2G07   17-6 

2530   17-7 

10,904  70  S 

22-2 

•84 

735 

777 

3*0 

1313    9-6 

-9359  68-6 

10,672  78-2 

10,489  77-0 

2950  21-8 

3133  23  0 

9,940  72  9 

66-6 

•28 

815 

073 

348 

14SL  10-7 

8614  61-9 

10,095  72-6 

8,795  03-8 

3805  27-4 

5105  86  7 

8.203  59-2 

66-6 

•87 

8.50 

102 

,, 

1338   10-0 

8410  63  0 

9,748  78-0 

8,188  61-4 

8602  27  -C 

5102  38  -^ 

7,632  57-1 

74-5 

•35 

860 

260 

847 

1171     9'2 

8315  66  '5 

9,486  74-4 

7,854  61-6 

3204  25-6 

4896   38-4 

7,841   57  5 

81-0 

•04 

S55 

444 

• 

1026     8'3 

8462  68-5 

9,488  76-8 

7,368  59'7 

2862  23-2 

4982  40-3 

6,910  55  9 

22-4 

•60 

705 

700 

323 

5128  38-7 

4389  83-1 

.9,617  71-8 

9,546  72-0 

8747  28-2 

3718  28-0 

8,791   66-2 

2-42 

•03 

382 

388 

350 

9207  CO-4 

3661   26-2 

12,928  92-6 

12,908  92-4 

1036     7-4 

1056     7'6 

12,319  S8  3 

3-46 

•S3 

455 

135 

407 

8331   56-7 

4844  82-8 

18,175  89-5 

18,268  90-1 

1540   10-5 

1462     9-9 

11,843  80-4 

111 

>3 

4S.r, 

441 

353 

7542  50-5 

4960  88-1 

12,492  88  6 

12,462  83-3 

2448   16-4 

2488  16-7 

11,863  79  3 

12-4 

•45 

448 

460 

368 

7037  47-3 

6197  84-9 

12,234  82  2 

12,152  81-7 

2046  17-8 

2728  18-3 

12,102  81-7 

6-63 

•75 

432 

385 

341 

8156  65-6 

4303  29-6 

12,468  86-1 

12,736  87-0 

2188   14  9 

1911   13-0 

10,819  78-9 

6-0 

•7 

440 

410 

366 

7424  50-6 

4922  88-6 

12,846  84-2 

12,529  85-5 

2318  15-8 

2139   14  5 

12,545  85  5 

11-3 

>•$ 

025 

480 

828 

6140  41-7 

6101  41-4 

12,?41  88-1 

12,882  87  4 

2497  10-9 

1S56  12-0 

P.T96  W8 

21-9 

3-7 

730 

700 

338 

8874  27/6 

6249  44-8 

10,123  71  9 

10,300  73  2 

3953  28-1 

3770  26-8 

?        J 

14-2 

2-8 

615 

080 

353 

6956  41-0 

6926  40-7 

11,880  8.1-7 

11,668  79-6 

2004  18-3 

2976  20  4 

10,984  71-4 

44' 

4-78 

525 

502 

357 

2458  17-0 

9921  68-4 

12,879  86-4 

12,066  83  2 

2121   14'ft 

2484   16  8 

18,866  92-1 

15-6 

2-71 

430 

476 

353 

4071   82-2 

8142  66-2 

12,813  88-4 

12,608  86  9 

1687  11-6 

1897  13  1 

14,344  98  9 

1-67 

•04 

000 

309 

208 

6957  47.8 

6tt6  89-6 

12,782  87-4 

18,416  92  1 

1836  12-6 

1152    7-9 

9,021  flfl'l 

4-61 

1-73 

790 

680 

304 

4117  28  4 

7268  60-0 

11,885  78-4 

12-.077  83-1 

8154  21-6 

2462  16-9 

9,679  60  5 

11-0 

2'8 

770 

700 

327 

2299  18-1 

6667  62:  7 

8,966  70-8 

9,831  78-7 

8699  29-2 

8834  26-3 

8,839  65  7 

7-2 

2-1 

690 

648 

320 

8297  26-2 

6881   64-7 

10,128  80;9 

10,288  82-2 

2394  19-1 

2234  17-8 

9,472  75-0 

1-4 

•85 

505 

422 

307 

6057  40-9 

6683  44-8 

12,690  86  7 

18,287  89-8 

2110  14-8 

1513  10  2 

11,464  77-5 

9-90 

2-21 

615 

560 

212 

4869  86-0 

6220  87-6 

10,096  72-6 

10,468  76-8 

8806  27-4 

8432  24-7 

9,226  60  3 

7-84 

2-03 

505 

565 

323 

6050  86-S 

4896  80-7 

9,446  66  :0 

9,646  66-6 

4870  84-0 

4T70  88-4 

8,168  67  0 

Ibid,  T.  69.  *  Ibid,  T.  81.  .   »  Ibid,  T.  93.  •  S 

inp,  7th  December,  1888.  •  Bnginttnny,  21st  November,  1 


1st  Augxiat,  18SO. 


6oo 


THE  PRACTICAL  PHYSICS  OF 


TABLE  CXX. 

"Alnwick  "  Portable,  Detailed  Calculation. 
;  8  m  MOB  ;  C  «:  -0384  ;  T. 

11,738 


Particulars— 

H,,  =  18,264;  A  =  23-2; 
making  :— 

w    ='24  x  (23-2  +  1.)  =  6-81 
H.  =  13,264  -  [6-81  x  (323  -  60)3 


Fire-box  :— 

Unit*  absorbed  per  lib.  =11,736  x(l  - 
sq.  ft.=  5,128  -f   4 


Available  units  remaining  in  gases  —  11,736  -6128 


6,128 
12,820 


Temperature  of  gaaes  on  leaving,  "~  +  323 


1/460- 


Intervals. 


O-'Oo 

•05  -'15 

•16-  -8 

•3-  -6 

•5-  '8 

•8^1-8 

Surface  in  section,    sq.  ft 

•05 

•1 

:16 

•2 

•8 

•6 

Entering  temperature     .  . 

1160" 

1896* 

1280* 

1186' 

980* 

8ST 

t>«  -0192  (T,  +  461)  ..     .. 
Transmission  per  1  dcg.,^ 
T,  +  T.  +  922  v  VV    \ 

86-88 
6-67 
1187 

86-65 
6-80 
1078 

83-42 
6-84 
067 

30-66 
6-27 
818 

27-84 
4-72 
666 

24  73 
4*12 
604 

2                 1250  / 
Degrees  of  diff.  =  T^  -  T« 

Transmission  per  sq.  ft  .  . 

7470 

6760 

5588 

4284 

3143 

2076 

,,          for  section.. 

878 

676 

888 

857 

043 

.108* 

Fall  of  temperature 

64 

116 

144 

147 

162 

179 

Final 

1396 

1280 

1136 

989 

827 

048 

Plotting  the  above  temperatures,  the  ordinate  corresponding  with  1105 
sq.  ft.  gives  705  deg.  as  the  final  temperature,  the  speed  at  which  is  22'33ft. 
per  second,  and  the  transmission  per  degree  3'69  units.  The  rates  of 
transmission  given  as  at  entering  and  leaving  tubes,  are  the  rates 
calculated  from  the  temperatures  at  these  points,  and  therefore  apply  to 
succeeding  sections,  starting  with  these  temperatures.  The  rates  at  the 
actual  points  of  entering  and  leaving  would  therefore  be  somewhat  in 
excess  of  those  tabled. 


THE  MODERN  STEAM  BOILER. 


60 1 


A    comparative    view    of    these    results    is    afforded    by  the 
following  diagram  : — 


2COO' 


1600 


1000 


Alnwick  (9 
Foden     S  mpla 
Compd 

Stf 


500 


It  is  apparent  from  a  review  of  results  that  none  of  the 
boilers  hitherto  introduced  have  attained  a  performance  which 
entitles  them  to  be  considered  as  even  approaching  finality  in 
their  design. 

Certainly  none  of  them  carries  out  to  any  degree  of  com- 
pleteness the  application  of  the  principles  discussed  in  this 
book,  although  there  are  evidences  of  attempts  having  been 
made  in  certain  examples  to  reach  a  more  thorough  applica- 
tion of  some  of  these  principles.  Attention  has  been  directed 
to  obtaining  more  perfect  combustion  in  some  forms  of  Babcock 
and  Wilcox  boilers,  in  the  later  Haythorn  and  Weir  designs, 
and  in  those  proposed  for  the  American  motor  car  as  illus- 
trated in  the  Mechanical  Engineer  of  9th  April,  1898,  and  by 
Professor  Watkinson  in  his  patent,  No.  13328  of  1898.  The 
spiral  movement  of  the  heated  currents  of  water  has  been 
provided  for  in  Dr.  De  Laval's  form  of  boiler,  and  this  inventor 
seems  also  to  have  appreciated  the  importance  of  forced  or 
accelerated  circulation  of  the  water.  The  boiler  patented  by 
Dagnell  and  Southey  (see  the  Mechanical  Engineer,  2nd  April, 
1898,  page  360)  also  shows  that  an  appreciation  of  the  value  of 
a  spiral  movement  of  the  water  is  beginning  to  dawn  upon 


602  THE  PRACTICAL  PHYSICS  OF 

inventors,  although  in  that  special  case  that  motion  is  utilised  for 
other  purposes  than  that  of  heat  transmission.  It  is  the  better 
utilisation  of  the  heating  surface  which  offers  the  most  promis- 
ing direction  in  which  improved  evaporative  results  may  be 
anticipated.  Both  water  and  gases  should  be  caused  where 
possible  to  travel  over  the  surfaces  with  a  spiral  movement,  and 
it  is  important  that  the  two  currents  should  move  in  opposite 
directions  and  at  suitable  velocities. 


APPENDIX   I. 

THE  modern  history  of  forced  draught  appliances  is  fully  described  and 
illustrated  in  the  following  publications,  which  may  be  consulted  for  many 
details  which  are  necessarily  omitted  from  this  work  : — 

Peclet,  "  Traite  de  la  Chaleur,"  chaps,  vi.  and  vii. 

C.  Wye  Williams,  "  Fuel  :  Its  Combustion  and  Economy,"  pp.  134-138. 

F.  J.  Rowan,  "The  Design  and  Use  of  Boilers,"  Engineering,  vol.  xxvi., 
pp.  164-283. 

F.  J.  Rowan,  "  Chimney  Draught  and  Forced  Combustion,"  Trans.  Inst. 
Engineers  &  Shipbuilders  in  Scotland,  vol.  xxxii.,  p.  109. 

Capt.  Hamilton  Geary,  Journal  Royal  United  Service  Instn.,  vol.  xxi.  (1877), 
P.  050. 

D.  K.  Clark,  "  The  Steam  Engine,"  etc.,  vol.  iv.,  pp.  667-676. 

,,  "  Railway  Machinery." 

W.  G.  Spence,  "  On  Forced  Draught."  Trans.  N.  E.  Coast  Inst.  Engineers. 
Jan.,  1888. 

I.  A.  F.  Aspinall,  "The  Draught  of  Locomotives."  Inst.  Mech.  Engineers. 
1893. 

Engineering  AY-ic's,  Xew  York.     June  7,  1890. 
Tlic  Engineer,  London.     January  23  and  February  6,  1891. 
Transactions  of  the  Inst.  Xaval  Architects  : 

1880.     Papers  by  J.  F.  Flannery. 
1883.  R.  T.  Butler. 


1884. 
1885. 
1886. 
1893. 
1894. 
1895- 


James  Hovvden. 

J.  T.  Milton  and  M.  H.  Robinson. 

R.  Sennet  and  James  Howden. 

J.  D.  Ellis. 

F.  Gross. 

W.  A.  Martin. 


A.  J.  Durston,  Trans.  Inst.  Marine  Engineers  (1865)  and  Proc.  Inst.  C.E., 
Vol.  cxix.,  p.  17. 

James  Howden,  "  Forced  Combustion  in  Steam  Boilers,"  Proc.  International 
Engineering  Congress,  1894,  Vol.  ii. 

J.  Patterson  and  M.  Sandison,  "  Forced  Draught,"  Trans.  N.  E.  Coast.  Eng., 
Vol.  ii.  (1886). 

M.  Paul,  "  Suction  Draught,"  Trans.  Inst.  Engineers  and  Shipbuilders  in 
Scotland,  Vol.  xl.  (1897). 

J.  Thorn,  "  Comparison  of  Systems,"  etc.,  Trans.  Inst.  Engineers  and 
Shipbuilders  in  Scotland,  Vol.  xxxix.  (1896). 

J.  C.  Hoadlcy,  "  \Vunn  Blast  Steam  Boiler  Furnaces,"  Wiley  and  Sons, 
New  York  (2nd  ed.). 


APPENDIX   II. 

LIST  OF  WRITINGS  ON  HEAT  TRANSMISSION. 

1690.  SIR  ISAAC  NEWTON. 

1818.  DULONG  AND  PETIT,  Ann.  Ch.  Phys.  [2],  vii.,  pp.  225-337. 

1822.  JOSEPH  FOURIER,  "  Theorie  Analytique  de  la  Chaleur  "  (Paris,  1822). 

1835.  POISSON,  "Theorie  Mathematique  de  la  Chaleur"  (Paris,  1835). 

,,  DESPRETZ,  Ann.  Ch.  Phys.  [2],  xix.,  97  ;  xxxvi.,  p.  422. 

1840.  E.  PECLET,  "Traite  de  la  Chaleur"  (3rd  Edn.,  Liege,  1844). 

1844.  WIEDMANN  AND  FRANZ,  Pogg.  Ann.,  Ixxxix.,  p.  497. 

1848.  T.  CRADDOCK,  "  Chemistry  of  the  Sceam  Engine"  (Birmingham,  1848). 

1858.  J.  GRAHAM,  Proc.  Lit.  and  Phil.  Soc.,  Manchester,  1858,  Feby. 

1859.  W.  J.  M.  RANKINE,  "  The  Steam  Engine  and  other  Prime  Movers." 
1864.  COLDING,  see  Min.  Proc.  Inst.  C.E.,  vol.  Ixxvii.,  p.  311. 

1867.  B.  F.  ISHERWOOD,  .see  "The  Steam  Engine,"  by  D.  K.Clark,  vol.  i.,p.  14. 

1871.  J.  CLERK  MAXWELL,  "Theory  of  Heat"  (London,  1871).. 

1875.  PAUL  HAVREZ,  Ann.  du  Genie  Civil,  1874. 

„  ,,  „          Etudes  sur  les  Chaudieres.a  Vapeur  (Liege,  1875). 

„  GOUILLAUD,  Ann.  Ch.  Phys.  [3],  xlviii.,  p.  47. 

„  ANGSTROM,  Pogg.  Ann.,  cxiv.,  p.  527. 

,,  OSBORNE  REYNOLDS,  Proc.  Lit.  and  Phil.  Soc.,  Manchester,  vol.  xiv.  (1875). 

1876.  HEUMANN,  Ann.  de  Ch.  et  Phys.  [3],  Ixvi.,  p.  185. 

1883.  G.  A.  HAGEMANN,  Min.  Proc/Inst.,  C.E.,  vol.  Ixxvii.,  pp.  311-322. 

„  A.  WlNKELMANN,  ,,  ,,  „  p.  468. 

1886.  J.  FLETCHER,  Engineering,  vol.  xlii.,  p.  69. 

1889.  C.  R.  LANG,  Trans.  Inst.  Eng.  and  Shipbuilders  in  Scot.,  vol.  xxxii.,  p.  287. 
„  D.  K.  CLARK,  "The  Steam  Engine,"  etc.,  vol.  i.,  pp.  13-81. 

„  „  ,,          Manual  of  Rules,  Tables,  etc.,  p.  465. 

1890.  J.  G.  HUDSON,  The  Engineer,  vol.  Ixx.,  pp.  449,  483,  523. 

„    Ixxvi.,  p.  107. 

„  J.  HIRSCH,  Bull,  de  la  Soc.  d'Enc.  pour  Indus.  Nat.,  vol.  v.,  p.  302. 

1891.  A.  F.  YARROW,  Trans.  Inst.  N.A.,  vol.  xxxii.,  p.  98. 

„  Louis  SER,  Traite  de  Physique  Industrielle,  vol.  i.,  pp.  225-227. 

1892.  A.  C.  KIRK,  Engineering,  vol.  liv.,  pp.  78,  333. 

1893.  A.  BLECHYNDEN,  Trans.  Inst.  N.A.  vol.  xxxv.,  p.  70. 

„  „  ,,  Engineer,  Ixxvi.,  pp.  98,  127  ;  Ixxxi.,  p.  509. 

Engineering,  Ivi.,  p.  74  ;  lx.,  p.  50. 

,,  A.  J.  DURSTON,  Trans.  Inst.  N.A.,  vol.  xxxiv.,  p.  130. 

,,  A.  WITZ,  Compt.  Rendus  de  1'Acad.  des  Sciences. 

,,  ,,          Min.  Proc.  Inst.  C.E.,  vol.  cviii.,  p.  473. 

1895.  JAMES  FOSTER,  "  Evaporation  by  Multiple  Effect  "  (2nd  Edn.,  Sunder- 

„  A.  NORMAND,  Trans.  Inst.  N.A.,  vol.  xxxvi.  [land,  1895). 

„  C.  E.  STROMEYER,  Engineering,  vol.  Iviii.,  p.  443. 

„  LORD  KELVIN,  Encycl.  Brit.,  9th  Edn.,  Article  Heat. 

„  T.  E.  STANTON,  Phil.  Trans.,  A.,  1897,  vol.  190,  pp.  67-88. 

1898.  J.  PERRY,  Trans.  Inst.  E.  and  S.  in  Scot.,  vol.  xlii.,  p.  63. 

„  G.  HALLIDAY,  Trans.  Inst.  E.  and  S.       „         „         p.  41. 

„  „         „        Engineer,  vol.  Ixxxvii.,  p.  473,  and  26th  Dec.,  1899,  p.  653. 

„  E.  M.  BRYANT,  Min.  Proc.  Inst.  C.E.,  vol.  cxxxii.,  p.  274. 

1901.  E.  C.  SCHMIDT,  Railroad  Gazette  (New  York),  vol.  xxxiii.,  pp.  408,  409 

604 


APPENDIX   III. 
ON  BOILER  INCRUSTATION  AND  CORROSION. 

THERE  is  perhaps  no  subject  connected  with  Engineering  Science  which 
at  the  present  time  commands  more  attention  or  causes  more  perplexity 
than  does  the  compound  subject  of  this  paper.  In  Marine  Engine  practice 
its  difficulties  are  most  keenly  felt  ;  and  of  itself  that  is  a  field  of  operation 
large  enough,  as  it  involves  interests  sufficiently  extensive  to  give  great 
importance  to  the  subject,  and  to  demand  the  utmost  exertions  of  engineers 
towards  the  solution  of  its  problems,  and  the  providing  of  remedies  or 
preventive  measures  against  the  ravages  of  what  is  an  active  and  powerful 
agent  in  the  destruction  of  their  works.  But  the  range  of  action  which  this 
destructive  agent  has  is  bounded  only  by  that  which  puts  a  limit  to  the 
use  of  steam,  and  hence  many  other  interests  besides  those  of  engineers 
are  involved  in  the  matter. 

The  state  of  general  information  about  this  subject  is  very  unsatisfactory, 
because  it  amounts  only  to  the  fact  that  obscurity,  or  at  least  uncertainty,  pre- 
vails. Yet  many  facts  of  the  greatest  interest  and  importance  have  been 
observed  and  noted,  and,  as  is  usual  in  such  cases,  there  are  some  men  who 
have  considered  these  in  the  light  of  their  own  experience  with  the  intelli- 
gence which  is  needed  in  order  to  turn  all  to  good  account.  As  the  subject  is 
partly  a  chemical  and  partly  a  mechanical  one,  it  demands,  in  order  that  it 
may  be  successfully  grappled  with,  a  combination  of  scientific  and  practical 
information  which,  in  consequence  of  defective  educational  methods,  has  not 
frequently  been  found  among  engineers. 

I  propose  to  myself  in  this  paper  the  simple  task  of  bringing  together  these 
scattered  facts  and  observations,  adding  to  them  in  whatever  measure  I  am 
able,  in  order  to  elucidate  if  possible  the  full  truth  of  the  matter.  The  course 
of  investigation  and  inquiry  which  have  been  called  forth  has  been  marked  by 
the  suggestion  of  various  remedies.  The  earlier  stages  have  produced  the 
recommendation  of  a  variety  of  empyrical  remedies  or  nostrums — substances 
which  have  been  proposed  apparently  for  every  conceivable  reason  except  an 
intelligent  perception  of  the  nature  of  the  action  to  be  counteracted,  and  con- 
sequently of  the  qualities  requisite  in  the  remedy.  A  list  of  these  applying  to 
Incrustation  is  given  in  a  paper  by  Mr.  James  Napier,  published  in  the  Proc.oJ 
the  Phil.  Soc.  of  Glasgow  (vol.  iv.,  1855-58),  who  gives  also  some  account  of 
the  more  rational  methods  proposed  in  his  day.  For  Corrosion  a  similar  list 
has  in  recent  times  appeared — too  large,  however,  to  quote  at  length  ;  and 
some  methods  of  working  have  been  proposed  which  have  been  more  or  less 
successful  under  special  circumstances,  but  all  partial  in  their  application. 
Of  these  are  the  endeavour  to  form  a  scale  of  salt  by  the  use  of  a 
proportion  of  sea  water,  the  use  of  zinc  in  the  boilers,  filtering  the  feed 
water,  etc. 

There  seems  to  be  in  some  quarters  the  idea  that  Incrustation  and  Corrosion 
of  Boilers,  inasmuch  as  in  general  they  both  result  in  the  destruction  of  the 
boilers,  are  one  and  the  same  action.  But  although  this  is  an  error,  and  the 
two  actions  are  very  dissimilar,  yet  they  are  so  often  united  in  effecting  the 
destruction  of  boilers  (and  almost  all  crusts  contain  iron),  and  are  so  often 
present  successively  in  the  same  boiler  (i.e.,  a  crust  being  formed  and  then 
decomposed  or  partially  decomposed,  with  injury  to  the  boiler),  that  an 

605 


606  APPENDIX. 

examination  which  did  not  include  a  notice  of  both  could  not  lay  claim  to  any 
degree  of  completeness. 

INCRUSTATION. 

A  few  years  ago  the  attention  of  all  concerned  was  exclusively  directed  to 
Incrustation,  its  evils  and  prevention.  The  evils  produced  by  it  are  numerous, 
for  boilers,  when  coated  with  crust,  quickly  accumulate  layers  of  this 
material,  which  is  a  bad  conductor  of  heat,  and  thus  are  not  only  hard  to 
steam,  requiring  a  large  excess  of  coal,  but  are  more  quickly  worn  out  and 
sometimes  suddenly  oxidised  or  "  burned,"  in  consequence  of  the  increased 
temperature  rendered  necessary  in  the  furnaces.  Dr.  J.  G.  Rogers,  of 
Madison,  U.S.,  in  a  paper  published  some  years  ago,  estimated  the  conducting 
power  of  crusts  as  compared  with  that  of  iron  as  i  is  to  37*5.  A  scale  ^ 
inch  thick,  he  says,  requires  an  extra  expenditure  of  15  per  cent,  more  fuel, 
and  this  ratio  increases  as  the  scale  is  thicker.  Thus  when  it  is  ^  inch,  60  per 
cent,  more  fuel  is  needed  ;  ^  inch,  150  per  cent.,  etc.  The  temperature  of  the 
heating  surface  of  the  boiler  must  be  raised  in  proportion  to  the  thickness  of 
scale.  Thus,  while  to  produce  steam  of  a  pressure  of  90  Ibs.,  water  must  be 
heated  to  about  320°  Fahr.,  and  this  can  be  done  in  clean  boilers  with  £-inch 
plates  by  heating  the  boiler  surface  to  about  325°,  if  £  inch  of  scale  intervenes 
between  the  shell  and  the  water,  it  will  be  necessary  to  raise  the  temperature 
of  the  heating  surface  to  about  700° — almost  low  red  heat.  Iron  oxidises  the 
more  rapidly  the  higher  the  temperature  at  which  it  is  kept,  and  at  any  heat 
above  600°  it  very  soon  becomes  granular  and  brittle,  and  is  liable  to  give 
way  under  pressure.  This  condition  predisposes  the  boiler  to  explosion,  and 
makes  expensive  repairs  necessary,  and  the  presence  of  scale  also  renders  the 
raising  and  lowering  of  steam  slower.  (Chem.  News,  vol.  xxvi.,  p.  17.)  The 
proper  circulation  of  the  water  is  also  interfered  with  by  the  presence  of 
crust.  Both  economy  and  durability  thus  require  the  absence  or  prevention 
of  crust. 

There  are  two  distinct  classes  of  boilers  which  are  subject  to  incrustation, 
and  these  are — 

1.  Land  boilers  using  natural  fresh  waters,  and 

2.  Marine  boilers  using  sea  water. 

i ."  There  is  no  doubt  that  the  quality  of  natural  fresh  waters  varies 
between  wide  limits,  from  rain  water  on  the  one  hand,  which  contains  no 
mineral  impurities,  to  that  of  highly  charged  mineral  and  chalybeate  springs 
on  the  other.  But  in  this  matter,  as  in  every  other,  extreme  or  exceptional 
cases  always  demand  exceptional  treatment,  and,  therefore,  we  shall  leave 
these  aside  and  consider  the  more  general  and  useful  aspect  of  the  subject. 

An  examination  of  the  analyses  of  waters  supplied  to  the  principal  manu- 
facturing towns  in  Britain  (such  as,  for  instance,  are  published  in  the  Report 
of  the  Registrar-General,  Vol.  VI.)  and  comparison  with  that  of  rivers  in  other 
countries,  demonstrates  that  no  better  general  or  average  illustration  of  this 
class  can  be  met  with  than  is  afforded  by  the  River  Clyde  water,  which  was 
in  general  use  in  this  city  and  neighbourhood  prior  to  the  introduction  of 
Loch  Katrine  water,  and  which  is  still  used  in  some  manufacturing  establish- 
ments. As  analysed  by  Dr.  Wallace  in  1848,  that  water  contained  the  follow- 
ing impurities,  which  are  here  tabulated  in  grains  to  the  gallon  : — 

CLYDE  WATER  AS  SUPPLIED  TO  GLASGOW  IN  1848. 

Carbonate  of  lime...         ...         ...         ...         ...         ...         ...  2*52 

Carbonate  of  magnesia    ...         ...         ...         ...         ...         ...  72 

Sulphate  of  lime -26 

Sulphates  of  potash  and  soda 1*94 

Chloride  of  magnesium -40 


APPENDIX.  607 

Chloride  of  sodium  ...         ...         ...         ...         ...         ...  -54 

Oxide  of  iron         ...         ...         ...         ...         ...         ...         ...  trace. 

Phosphate  of  lime  and  alumina  -31 

Silica  -28 

Organic  matter      -89 


Total       7-86 

Dr.  Wallace  (to  whose  courtesy  I  am  indebted  for  the  above  and  other 
information  on  this  subject,  and  for  much  valuable  assistance  in  connection 
with  this  paper)  has  informed  me  that  the  total  amount  of  solid  matter  in 
solution  in  this  water  increased  in  quantity  gradually,  and  that   in    1854  it 
amounted  to  10  or  n  grains  per  gallon. 

The  incrustation  formed  upon  ordinary  steam  boilers  working  in  mills  at 
from  15  to  20  Ibs.  per  square  inch  pressure  of  steam  (above  the  atmosphere) 
and   using   that   water,   analysed   by    the   same  authority,  is  found  to  con- 
sist  of  : — 

Per  cent. 
Carbonate  of  lime  ...         ...         ...         ...         ...         ...       66-oo 

Magnesia    ...         ...         ...         ...         ...         ...         ...         ...         6^05 

Sulphate  of  lime   ...         ...         ...         ...         ...         ...         ...         4^28 

Water,  with  traces  of  carbonic  acid     872 

Oxide  of  iron,  alumina,  and  phosphate  of  lime          5-85 

Silica  8'io 

Organic  matter      roo 


lOO'OO 

This  crust,  which  is  of  a  dark  brown  colour,  and  is  hard,  forms  rapidly 
on  the  interior  of  the  boilers,  and  is  difficult  to  remove.  But  it  has  been 
found  that  by  a  moderate  use  of  soda  ash,  this  formation  is  readily  stopped  or 
held  in  check. 

The  quantity  of  soda  ash  used  in  a  pair  of  boilers — one  30  horse-power, 
6  ft.  6  diam.  X  21  ft.  long  ;  one  40  horse-power,  7  ft.  6  diam.  X  27  ft.  long — 
which  together  require  about  9700  gallons  of  water  per  week,  is  6  Ibs.  per 
week  in  both  boilers.  This  is  dissolved  in  water,  and  fed  into  the  two  boilers 
once  a  week. 

The  action  of  this  soda  ash  or  carbonate  of  soda,  under  these  circumstances, 
is  a  very  interesting  one,  though  perhaps  not  \vell  understood  by  those  using 
the  substance  in  this  way.  Sulphate  of  lime  is  decomposed  by  its  means  and 
precipitated  as  carbonate,  while  a  soluble  sulphate  of  soda  is  formed.  The 
neutral  carbonate  of  lime  is  likewise  produced  by  reaction  from  the  bicarbon- 
ate in  solution,  and,  as  thus  formed,  it  will  not  adhere  to  the  boiler  surfaces, 
but  separates  as  a  loose  powder  or  mud,  which  can  be  blown  out  of  the 
boilers  or  otherwise  removed  as  sludge.  In  those  boilers  under  notice  the 
quantity  of  this  sludge  is  found  to  be  three  pails  full  from  each  boiler  every 
three  months. 

It  has  been  found,  however,  that  where  the  neutral  carbonate  of  lime 
is  produced  slowly  by  the  action  of  heat — which  drives  off  part  of  the 
carbonic  acid  from  the  bicarbonate  existing  either  in  solution  in  the  water  or 
as  a  solid  already  deposited  upon  the  boiler  surfaces — that  in  this  case 
the  neutral  carbonate  possesses  the  property  of  being  able  to  adhere 
firmly  of  itself  to  the  boiler  plates.  It  seems  to  be  in  this  case  partially 
crystalline.  Thus,  the  special  advantage  arising  from  the  employment 
of  soda  ash  is  that  it  decomposes  the  bicarbonate  rapidly,  probably  because  of 
the  presence  of  some  soda  uncombined  in  the  ash,  and  that  the  neutral 
carbonate  is  precipitated  as  a  loose  powder,  which  will  not  adhere  unless, 
fused  or  agglomerated  by  means  of  some  other  substance. 


608  APPENDIX. 

Concerning  this  latter  point,  M.  Bidard,  of  Rouen  (a  French  chemist 
who  has  written  largely  on  this  subject  in  the  Annales  Industrielles,  and  in  a 
Belgian  journal  entitled  the  Moniteur  de  la  Brasserie),  has  informed  me 
that  his  numerous  examinations  of  boiler  incrustations  have  demonstrated  the 
fact  that  the  presence  of  organic  matter  is  necessary  for  the  formation  of 
boiler  crusts,  which  consist  essentially  of  carbonate  of  lime.  Such  crusts 
he  has  produced  artificially,  in  order  to  verify  his  theory. 

He  says  in  one  letter,  "  Lorsque  le  carbonate  de  chaux  neutre  se  depose  au 
sein  de  1'eau  que  le  tenait  en  dissolution  s'il  rencontre  de  la  matiere 
organique  en  dissolution,  bois,  extrait  de  teinture,  savon  de  resine, 
jucus,  &c.,  &c.,  il  s'y  combine  et  forme  avec  elle  une  combinaison  insoluble. 
Elle  se  depose  sur  les  parois  de  la  tole  (toujours  plus  chauds  que  1'eau), 
elle  s'agglomere  a  une  pression  de  6  atmospheres,  par  exemple,  ou  160°  de 
chaleur,  forme  une  pate  qui  ciiit  comme  de  la  pate  a  farine  et  produit 
1'incrustation.  J'ai  en  ma  possession  des  incrustations  qui  contiennent 
16  pour  cent,  de  matieres  organiques." 

Fresenius,  however,  quoted  by  Dr.  Wallace  (Proc.  Phil.  Soc.,  Glasgow; 
vol.  iv.,  p.  319),  without  specially  noticing  the  presence  of  organic  matter,  has 
attributed  a  cementing  property  to  sulphate  of  lime,  which  he  always 
found  present  in  boiler  crusts. 

M.  Bidard's  explanation  thus  applies  specifically  to  those  crusts  which 
contain  carbonate  of  lime  and  no  sulphate,  for  it  is  probable  that  where 
sulphate  is  present  it  possesses  agglomerating  power  of  itself  sufficient  to 
render  the  presence  of  organic  matter  unimportant  in  these  instances.  This 
is  demonstrated  in  examples,  in  some  marine  boilers  for  instance,  where 
crusts  are  formed  without  organic  matter  being  present  in  appreciable 
quantity,  of  which  the  analyses,  on  page  609,  by  Dr.  Wallace  are  specimens. 
But  M.  Bidard's  remarks  show  that  soda  ash  might  be  used  with  muddy 
water,  such  as  canal  water  for  instance,  and  yet  a  hard  incrustation  would 
form.  In  such  a  case  there  would  be  no  preventive  but  the  use  of  a  filter  for 
all  the  water  passing  into  the  boiler  in  addition  to  the  use  of  soda  ash 
there. 

The  use  of  too  much  soda  ash  is  injurious  in  its  effects,  as  the  excess 
boils  up  and  passes  over  in  the  steam  to  cylinders  and  pumps,  where  it  clogs 
the  pistons,  and  otherwise  interferes  with  proper  working  by  making  com- 
binations with  the  oils  and  greasy  matters  employed  in  the  machinery.  The 
lavish  use  of  oils  and  grease,  of  course,  intensifies  this  action  where  it  is  pre- 
sent, and  it  has  been  found  that  the  carbonate  of  lime  itself  has  passed 
over  from  the  boiler  with  the  steam  and  has  entered  into  combination 
with  the  grease  where  enough  was  to  be  found.  "  La  decomposition  de 
corps  gras  dont  vous  me  parlez,"  writes  M.  Bidard,  "  ne  va  pas  jusqu'au 
charbon  seulement,  il  se  produit  la  une  combinaison  de  corps  gras  et 
de  chaux  provenant  de  carbonate  de  chaux,  autrement  dit  savon  de  chaux, 
tres  prejudiciale  pour  la  tole  des  chaudieres.  J'ai  etc  dernierement 
temoin  et  expert  d'un  fait  tres  curieux.  Le  carbonate  de  chaux  entraine 
par  la  vapeur  est  arrive  dans  le  corps  de  pompe — il  a  forme  avec  la 
graisse  un  savon  de  chaux  tellement  abondant  et  dur  que  la  piston  s'est 
subitement  arrete." 

All  that  is  needed,  however,  in  working  with  soda  ash  is  a  little  in- 
telligent care,  and,  as  the  matter  is  simple,  a  system  of  working  is  soon 
arrived  at.  As  an  example,  I  take  the  boilers  already  mentioned  at 
Barrowfield.  Under  ordinary  circumstances  the  manager  proceeds,  as  I  have 
said,  blowing  out  the  boilers  once  in  three  months.  When,  however,  there 
is  a  fresh  or  "  spate  "  in  the  river  the  quantity  of  inorganic  solids  in  the  water 
is  proportionately  less,  and  the  quantity  of  soda  ash  introduced  is  in 
consequence  diminished.  Muddiness  in  the  water,  seen  in  the  gauge  glasses 
is  a  sure  test  if  too  much  is  being  used,  and  when  this  is  noticed  and 


APPENDIX.  609 

acted  upon  no  inconvenience  from  material  passing  over  to  the  cylinders  is 
found  to  result. 

An  interesting  fact  may  be  mentioned  in  connection  with  this  part  of  the 
subject  and  as  illustrating  how  calcareous  waters  sometimes  contain 
soluble  matters  which  themselves  counteract  their  crust-forming  ingredients. 
The  boilers  of  an  engineering  works  in  M'Neill  Street  use  the  water 
drawn  from  the  Clyde  at  a  point  which  is  considerably  below  Barrow- 
field,  the  water  being  contaminated  by  the  refuse  from  print  works  and 
other  factories  discharged  into  it  between  the  two  points. 

A  comparative  estimation,  by  Dr.  Wallace,  of  the  qualities  of  the  water 
from  both  localities  is  here  tabulated  : — 

I.  From          II.  From 
Barrowfield.      M'Neill  St 

Total  solids  per  gallon        8*96     ...  15*12 

Insoluble  in  water,  carbonates  of  lime  and 

magnesia,  silica,  etc.       ...         ...         ...  2*94     ...  378 

Soluble  salts 3-92     ...  672 

Organic  matter,  etc.  (loss  by  ignition)    ...  2'io     ...  4-62 

Alkalinity  expressed  in  soda         -014  ...  -056 

The  marked  difference  in  amount  of  total  solids  per  gallon,  and  in  the 
amount  of  soluble  salts  and  degree  of  alkalinity,  shows  that  a  decided 
change  has  been  effected  in  the  water  by  the  time  it  reaches  M'Neill 
Street.  In  using  it  in  the  boilers  there,  it  is  only  after  a  considerable 
time,  and  in  corners  of  the  boiler,  that  a  crust  is  formed.  The  ingredients  of 
the  water  seem  in  general  to  react  naturally,  and  in  regular  working  only  a 
deposit  of  loose  mud  collects,  which  is  blown  out  of  the  boilers  each  morning. 
The  composition  of  the  crust,  as  analysed  by  Dr.  Wallace,  is  given  below, 
but  a  full  analysis  of  the  water  would  be  required  in  order  to  show  what 
re-actions  took  place  in  working  : — 

Carbonate  of  lime          64-98 

Sulphate  of  lime 9-33 

Magnesia...         ...         ...         ...         ...         ...         ...  6*93 

Combined  water...         ...         ...         ...         ...         ...  3-15 

Chloride  of  sodium        ...         ...         ...         ...         ...  '23 

Oxide  of  iron       ...         ...         ...         ...         ...         ...  1-36 

Phosphate  of  lime  and  alumina           372 

Silica         6-60 

Organiq  matter r6o 

Moisture  at  212°  F.  2-10 


lOO'OO 

The  use  of  soda  ash  as  a  preventive  of  the  formation  of  incrustations 
in  boilers  working  with  calcareous  waters  is  so  rational  and  simple  that 
it  has,  from  a  comparatively  early  date,  commended  itself  to  chemists, 
and  has  been  by  them  repeatedly  proposed  to  engineers.  The  material 
itself  possesses  for  the  majority  of  cases,  where  such  is  called  for,  all  that  it  is 
requisite  an  anti-incrustator  should  possess,  while,  if  used  with  average 
care  and  intelligence,  it  is  not  capable  of  acting  destructively.  Its  application 
is  simple,  as  it  may  be  added  in  solution  either  periodically — as  in  the 
case  of  the  boilers  quoted — or,  better,  regularly  and  steadily  in  fixed  proportion 
to  the  quantity  of  water  fed  into  the  boiler,  after  the  manner  proposed 
by  Mr.  James  Napier  in  the  paper  already  alluded  to.  There  is  also  no 
reason  why  it  should  not  be  added  in  proper  proportion  to  the  water  in  the 
feed  tank  or  cistern,  instead  of  being  put  into  the  boiler.  In  this  way,  as  the 
re-action  between  soda  ash  and  sulphate  of  lime  does  noc  require  a  high 
temperature  or  pressure,  the  precipitated  carbonate  of  lime  could  be 


6io  APPENDIX. 

arrested,  and  comparatively  pure  water  fed  into  the  boilers,  frequent 
blowing-off  being  also  rendered  unnecessary. 

With  waters  containing  only  a  little  sulphate,  and  chiefly  carbonate  of 
lime,  it  would  be  necessary,  however,  to  introduce  the  soda  salt  into  the 
boiler,  as  a  temperature  of  100°  Cent.  (212°  Fah.)  is  requisite  for  the  decom- 
position of  the  bicarbonate  of  lime. 

A  short  examination  of  the  various  remedies  against  incrustation  which 
have  been  proposed  will  not  be  uninteresting,  although  it  results  in  the  con- 
viction that  most  of  them  are  unsatisfactory. 

Oxalate  of  soda  and  tannate  of  soda  were  proposed  by  Dr.  Rogers  in 
America,  in  order  to  form,  by  decomposition  of  the  lime  salts,  insoluble  oxalates 
and  tannates  ;  but  these  would  seem  to  increase  the  amount  of  solid  matter 
precipitated,  and,  although  proposed  some  years  ago,  to  have  been  little  used. 

Lime  and  zinc  have  been  used  with  some  degree  of  success,  but  their 
action  is  confined  to  combining  with  the  carbonic  acid  of  the  bicarbonate 
of  lime.  On  sulphate  of  lime  they  have  no  action. 

The  object  in  view  in  the  proposed  use  of  starchy  and  gelatinous  matters 
has  been  to  prevent  scale  forming,  by  enveloping  the  precipitated  or 
crystallised  solids  with  gelatinous  covering,  and  so  to  delay  their  settling 
by  diminishing  their  weight.  But  M.  Bidard's  observations  on  the  effects  of 
the  presence  of  organic  matters  (especially  in  so-called  "  anti-incrustators,"  or 
compounds  for  preventing  incrustation)  at  once  sweep  the  field  of  all 
remedies  of  an  organic  composition,  proving  them  to  be  injurious  by  doing 
the  very  thing  which  they  are  supposed  to  prevent. 

Referring  to  this  point,  he  says,  "Je  connais  a  Rouen  une  chaudiere  de 
la  force  de  30  cheveaux  qu  depuis  1852,  n'a  subi  aucune  reparation  aucune 
avarie.  Elle  inarche  cependant  alimentee  par  de  1'eau  calcaire,  le  netoyage 
ne  donne  que  de  la  boue,  jamais  de  calcin  adherent — il  n'enire  duns  In 
chaudiere  anemic  substance  orgnniqiic." 

Still,  however  useful  as  a  precaution  where  the  admission  of  extraneous 
organic  matter  can  be  prevented,  this,  as  a  system  of  preventing  incrustations, 
manifestly  fails  where  the  water  contains  organic  matter  in  solution. 

Sal-ammonia,  proposed  by  Ritterbrandt,  and  hydrochloric  acid,  are  both 
open  to  the  objections  that  their  preventive  action  is  only  partial,  and  that 
they  have  the  power  of  seriously  injuring  the  boilers  and  connections. 

Crude  pyroligneous  acid  has  been  suggested  for  action  upon  carbonates 
alone,  while  petroleum  has  been  extensively  used  in  the  United  States  with  a 
measure  of  success,  not  only  in  preventing  incrustations,  but  also  in  removing 
those  already  formed.  Its  action  has  not  as  yet  been  investigated,  as  far  as  I 
am  aware,  but  it  is  probable  that  its  effects  are  clue  to  decomposition  of 
hydrocarbons.  This  seems  to  be  borne  out  by  a  report  by  the  Chief  Engineer 
to  the  Steam  Boiler  and  Inspection  Coy.  of  Hartford,  U.S.  (an  extract  from 
which  appeared  in  the  Engineer),  who  states  that  "  petroleum  works  better 
where  sulphate  of  lime  predominates  than  in  waters  impregnated  with 
carbonate  of  lime.  We  would  not,"  he  says,  "  advise  it  in  connection  with 
this  latter."  This  simple  fact  renders  it  useless  in  the  majority  of  boilers 
using  fresh  water  in  this  country. 

Soap  acts  upon  both  carbonate  and  sulphate  of  lime,  but  the  quantity 
appears  to  be  increased  by  the  formation  of  lime  soap,  and  thus  the  boiler  is 
made  filthy ;  a  corrosive  crust  is  sometimes  formed,  and  priming  and  other 
evils  also  result  from  its  use. 

Recently  a  substance  called  "  Burfitt's  Composition  "  has  been  patented 
for  the  prevention  of  boiler  incrustation,  but  it  has  been  found  to  consist 
essentially  of  organic  matters,  and,  moreover,  has  rather  increased  than  prevented 
incrustation  where  it  has  been  used.  (See  Jour.  Cliem.  Soc.,  Jan.,  1876,  p.  134.) 

Two  other  methods  of  prevention  have  also  been  devised,  and  seem  to  be 
founded  upon  the  fact  which  Professor  Mills  informs  me  was  first  observed 


APPENDIX.  6n 

by  J.  Y.  Buchanan  (Proc.  Royal  Soc.  of  London,  1873-74,  vo'-  xxii.,  pp.  192  and 
483),  that  barium  chloride  decomposes  sulphates  and  liberates  the  carbonic 
ac  d  in  water. 

One  of  these,  called  u  De-Haen's  Process,"  which  consists  in  the  use  of 
barium  chloride  and  milk  of  lime,  is  now  extensively  used  in  Austria  and  in 
Krupp's  Works  in  Prussia.  A  recently  published  statement  of  the  compara- 
tive cost  of  working  on  this  system,  and  with  water  containing  gypsum, 
without  an  added  reagent,  shows  that  to  purify  33  cubic  metres  of  water 
when  containing  5  parts  gypsum  in  100,000,  the  cost  is  6d.,  and  when 
containing  30  parts  gypsum  the  cost  is  38.  Practical  working  writh  this 
process  for  12  months  with  one  or  two  boilers  (it  does  not  appear  very 
clearly  whether  one  or  two)  showed  an  increase  of  expenditure  amounting 
to  500  florins,  against  which  was  to  be  placed  the  saving  in  fuel  resulting 
from  absence  of  incrustation,  and  reduced  repairs  from  the  same  cause,  the 
value  of  these  however  not  being  stated.  (Dingier  Polyt.  Jour.,  ccxvii.,  338  ; 
Client.  SOL.  Join:,  No.  clxi.,  p.  799.) 

The  analyses  (given  March,  1876,  Client.  Soc.  /.,  No.,  clix.,  p.  450)  of 
deposits  which  have  been  found  to  accumulate  in  the  steam  pipes,  etc.,  where 
these  processes  have  been  used,  impress  us  with  the  idea  that  these  methods 
are,  however,  open  to  some  serious  objections  in  practical  working  on 
account  of  the  formation  of  salts  of  barium. 

There  is,  however,  one  system  of  working  which  has  yet  to  stand  its  trial, 
but  which  it  is  perhaps  not  extravagant  to  consider  as  inseparably  connected 
with  the  advancement  of  engineering  science  and  appliances  upon  which 
alone  it  depends.  That  is  the  working  of  land  boilers  in  connection  with 
surface  condensers,  and  so  supplying  them  with  pure  water.  No  incrustation 
is  possible  with  this  method,  and  its  theoretical  advantages  in  point  of 
economy  seem  to  justify  the  belief  that  its  present  limited  adoption  will 
prove  merely  the  precursor  to  its  more  general  introduction.  It  becomes  of 
all  the  more  importance  in  view  of  the  extended  use  of  sectional  or  water- 
tube  boilers,  because  with  these,  on  account  of  small  water  spaces,  no  mere 
preventive  measures  against  the  formation  of  incrustation  suffice.  Solid 
matters  ought  to  be  excluded  from  all  such  boilers. 

2.  It  is  necessary,  in  connection  with  incrustation,  to  consider  marine 
boilers  working  with  sea-water,  because  although  modern  systems  of  marine 
engine  practice  with  compound  engines  and  surface  condensers,  wherever 
these  have  been  adopted,  have  banished  incrustations  ;  yet  these  systems 
have  not  yet  been  universally  adopted,  and  there  is  even  a  disposition  with 
some  to  return  to  the  regime  under  which  incrustation  held  sway.  The  evil 
effects  of  incrustation  make  themselves  felt  with  multiplied  force  in  marine 
boilers,  because  of  the  great  rapidity  with  which  the  crusts  form,  in  conse- 
quence of  the  large  quantity  of  solids  contained  in  the  water.  I  am  informed 
by  Mr.  Tookey,  of  the  Royal  School  of  Mines,  that  British  Channel  water 
contains  2467  grains,  and  North  Sea  water  2408  grains  in  the  gallon  ;  and  it 
has  been  shown  by  Mr.  James  R.  Napier,  F.R.S.  (Proc.  Phil.  Soc.  Glasgow, 
vol.  iv.,  p.  281),  that  sulphate  of  lime  begins  to  deposit  before  one  half  of  the 
water  is  evaporated. 

In  addition  to  this  rapidity  of  formation  of  crust,  the  space  at  command 
for  storage  of  fuel  is  limited.  Large  quantities  of  chemical  reagents  cannot 
for  a  similar  reason  be  carried  ;  and  because  of  the  confined  space  in  which 
boilers  and  men  working  at  them  are  placed  on  board  ship,  the  results  of  an 
accident  to,  or  the  destruction  of,  the  boilers  are  serious  ;  while  great 
difficulty  is  also  experienced  in  getting  repairs  effected  in  foreign  ports 
generally.  All  these  considerations  render  it  of  the  greatest  importance  that 
marine  boilers  should  be  freed  from  incrustation.  Besides  these,  there  are 
reasons  connected  with  the  formation  of  sea-water  scale  which  render  its 
presence  in  boilers  undesirable. 

X2 


612  APPENDIX. 

Considered  from  a  chemical  point  of  view,  the  problem  of  preventing 
incrustation  in  these  boilers  appears  to  be  similar  to  that  experienced  with 
land  boilers,  inasmuch  as  the  substances  composing  the  crusts  are  similar  in 
both  cases,  although  differing  in  their  proportions  in  the  formations.  No 
doubt,  as  we  have  seen,  soda  ash  is  the  best  chemical  preventive,  where  that 
substance  has  to  be  used  in  ordinary  circumstances,  but  the  comparatively 
enormous  quantity  of  solid  matters  present  in  sea-water  causes  the  use  of 
soda  ash  to  be  attended  with  so  many  inconveniences,  and  so  much  expense, 
as  to  render  it  here  practically  useless.  In  these  circumstances  it  has  to  be 
combined  with  blowing  off  from  the  boiler  in  order  to  get  rid  of  the  solids, 
it  being  necessary,  as  Mr.  J.  R.  Napier  showed,  to  blow  off  T]Q  of  the  feed 
water,  and  neutralise  the  sulphate  of  lime  in  T%  with  soda.  The  loss  of 
heat  from  this  blowing  off  is  considerable,  and  it  is  combined  with  the 
cost  of  the  large  quantity  of  soda  required  for  neutralising.  Yet  this  process 
is  not  worse  than  the  ordinary  mechanical  one  of  discharging  the  saturated, 
or  what  is  supposed  to  be  the  saturated,  water  from  the  boilers  which  has 
been  most  generally  resorted  to.  In  this  case  the  indications  of  the  salino- 
meter  are  depended  upon,  and  fully  T5o  of  the  feed  water  have  to  be  dis- 
charged, little  of  its  heat  being  utilised.  With  regard  to  this  Mr.  Jas.  R. 
Napier  has  said  of  the  example  of  a  vessel  whose  boilers  worked  at  a  tempera 
ture  of  270°  that  "  a  quantity  of  fuel  equal  to  15^  per  cent,  of  that  which 
produces  evaporation  is  consumed  by  the  ordinary  blowing-off  method  in 
order  to  prevent  crust,  and  this  amount  increases  with  the  temperature." 

The  salinometer  might  prove,  and  perhaps  has  often  proved,  a  fallacious 
test,  for  if  it  were  applied  after  a  large  quantity  of  the  solids  had  been 
precipitated  from  the  water,  it  would  deceive  the  engineer  by  showing  a  less 
density  than  had  existed  previously,  and  thus  mislead  him  as  to  the  state  of 
the  boilers  and  of  the  water.  In  result  it  has  been  always  necessary  to  chip 
and  hammer  away  scale  from  the  interior  of  marine  boilers  worked  with  sea- 
water  to  an  extent  not  advantageous  to  them. 

Undoubtedly  the  most  sensible  and  efficacious  method  of  preventing 
incrustation  in  these  boilers  is  to  work  with  fresh  water.  This  has  been 
rendered  possible  in  many  instances  by  the  introduction  of  the  Surface 
Condenser  into  practical  working,  and  no  doubt  the  desire  to  avoid  the  evils 
of  Incrustation  has  operated  in  bringing  about  the  introduction  of  that  system 
which  is  at  present  the  most  general  in  marine  engineering.  On  the  other 
hand,  however,  the  commencement  of  this  era  in  engineering  practice  has 
been  the  introduction  of  engineers  to  all  the  evils  and  difficulties  of  Corrosion. 

Before  dismissing  the  subject  of  Incrustation,  I  wish  to  direct  attention  to 
the  following  analyses  and  notices  of  the  decompositions  which  take  place  in 
sea  water  in  boilers  during  the  formation  of  crusts,  as  these  throw  consider- 
able light  on  the  subjtCL  of  Corrosion.  The  following  analysis  of  Black  Sea 
water  was  given  me  by  the  late  Professor  Penny.  I  quote  it  only  as  showing 
the  various  ingredients  contained  in  sea-water,  as  I  have  no  means  of 
ascertaining  its  accuracy  now — 

Black  Sea  water,  sp.  gra.          1*01365 


Chloride  of  Sodium  14-020 

„  Potassium -190 

„  Magnesium  1-310 

Bromide  of  Magnesium            -005 

Sulphate  of  Lime  '105 

„  Magnesia 1-470 

Carbonate  of  Lime  -365 

„  Magnesia -209 

Total  salts  in  parts  per  1000  17*674 


APPENDIX.  613 

The  following  analyses  were  made  by  Dr.  Wallace  :  Nos.  I,  2,  4  and  5,  for 
a  paper  of  his  on  Boiler  Incrustation  (Proc.  Phil.  Soc.  Glasgow,  vol.  iv.,  p.  317) 
published  some  years  ago  ;  the  others  were  kindly  undertaken  for  me  along 
with  other  investigations  inserted  in  this  paper. 

No.  6  differs  from  the  rest  in  being  merely  a  deposit.  I  have  arranged  them 
in  tabular  form,  in  order  to  show  as  far  as  possible  their  relation  to  one 
another  as  having  been  formed  at  different  pressures  of  steam  — 

ANALYSES  OF  BOILER  CRUSTS  AND  DEPOSITS. 

No.  I.      No.  2.      No.  3.      No.  4.      No.  5.      No.  6.     No.  7. 

Sulphate  of  Lime        ......  33'95  66-88  6977  74-21  72-85  57-34  76-83 

Magnesia          .........  4005  18-96  15-75  14-95  I3'i8     1-94  r8i 

Carbonate  of  Lime     ......     —  3'44  '34 

Common  Salt  ........  traces,  traces.     -99  2-04  2-16     172  2-24 

Phosphate  of  Lime,  Alumina  )      1-33  -50     1-14  1-34  2-40 

and  Oxide  of  Iron       ...           j  "22  -   27-04  13-76 

Silica     ............  traces,  traces.     -16  -57  -80     7-60  2-24 

Ir66    8'2*      6'89      *V     «o     378 


loo-oo  loo-oo  99-72  loo-oo  loo-oo  99-94  100-66 

No.  i  is  from  the  Cunard  steamer  Asia,  probably  worked  at  about  4  or  5  Ibs. 

per  square  inch  pressure  of  steam. 

No.  2  is  from  the  King  Orry,  worked  at  about  5  to  10  Ibs.  pressure. 
No.  3  „  Propontis,  „  „         10        „  ,,     Old  boilers. 

No.  4          „          Cosmopolitan,      „  „    10  to  15    „  ,, 

No.  5          „          Source  unknown  „  ,,(?)i5to2OM  „ 

No.  6  „  Propontis,  „  ,,        150        „  ,,  Deposit 

before  sea-water  was  fed  into  Boilers. 
No.  7  is  from  the  Propontis,  worked  at  about  150  Ibs.  pressure,  Crust  after  sea- 

water  was  fed  into  Boilers. 

Dr.  Wallace,  in  his  paper  quoted  above,  remarks,  "  These  crusts  differ  from 
the  insoluble  matter  obtained  ,by  simply  evaporating  sea-water  in  open  vessels, 
for  that  contains  nearly  four  times  as  much  carbonate  of  lime  as  carbonate  of 
magnesia,  while  the  crusts  contain  a  large  quantity  of  magnesia,  and  little  or 
no  carbonate  of  lime.  The  decomposition  of  soluble  magnesian  salts  by 
carbonate  of  lime  under  the  influence  of  a  liquid  boiling  at  a  high  temperature 
(say  270°)  is  exceedingly  interesting.  Sulphate  of  magnesia  and  carbonate  of 
lime  boiled  with  water  under  ordinary  circumstances  do  not  re-act  upon  each 
other  in  the  slightest  degree  ;  but  it  is  evident  that  the  result  is  brought  about 
under  pressure.  The  re-action  with  oxide  of  manganese,  which  is  isomorphous 
with  magnesia,  is  exactly  similar,  and  is  taken  advantage  of  in  the  recovery  of 
the  manganese  used  in  the  preparation  of  chlorine,  as  practised  at  the  St. 
Rollox  Chemical  Works. 

"  Again,  the  condition  in  which  the  magnesia  occurs  is  peculiar.  We  should 
expect  a  basic  carbonate,  but  I  find  little  more  than  a  trace  of  carbonic  acid  in 
any  of  the  crusts.  (In  No.  I  it  was  -28).  The  magnesia  exists  essentially  as 
the  hydrate.  The  sulphate  of  lime  appears  to  occur  as  the  hydrate  described 
by  the  late  Professor  Johnson,  as  having  been  found  by  him  in  a  distinctly 
crystallised  condition  in  a  high-pressure  steam  boiler,  its  composition  being 
represented  by  the  formula  2(CaOSO3)  +  HO."  This  fact  is  stated  by  Gmelin, 
Handbook  of  Client.,  Vol.  Hi.,  p.  2OI.1 

1  Under  the  head  Di-hydrated  Sulphate  of  Lime,  Gmelin  says  :—  This  compound  was  deposited 
from  the  water  in  a  boiler  which  was  working  under  a  pressure  of  two  atmospheres  ;  it  formed 
a  greyish  granular  mass  of  specific  gravity  2-757,  appearing  under  the  microscope  in  the  form  of 


614  APPENDIX. 

Recently  these  results  have  been  verified  by  the  independent  investigations 
of  Dr.  Ferd.  Fischer  (published  in  Dingl.  Polyt  J.,  ccxii.  208-220,  and  noticed 
in  Chem.  Soc.  Jour.,  Oct.,  1874,  vol.  xii.,  p.  1021),  who  has  proved  from  a 
number  of  analyses  that  various  decompositions  of  the  salts  contained  in 
waters  take  place  under  the  influence  of  elevated  temperature  and  pressure. 
Fischer  quotes  various  authorities  to  show  that  gypsum  gives  off  nearly  half 
its  water  of  crystallization  at  temperatures  up  to  100°  (C.),  and  further  pro- 
portions at  higher  temperatures,  so  that  its  solubility  is  considerably  diminished. 
Above  140°  ic  becomes  totally  insoluble  in  sea-water,  and  at  a  lower  tempera- 
ture in  fresh  water,  and  hence  is  deposited  as  an  anhydride.  It  is  more  easily 
soluble  in  water  containing  sodium  or  magnesium  chloride  in  solution  than  in 
pure  water.  The  effect  of  pressure  on  its  solubility  and  that  of  other  salts  is 
shown  by  the  following  table  of  analyses  of  water  from  boilers  : — 

Taken  with  Mud  when 
One  litre  of  Water  contains — At  3  atmos.  At  1.5  atmos.  blowing  off  Boiler. 

Ca  SO4  (Ca  O,SO3)  0-885  gram.  1-136  gram.  3-028  gram. 

Ca  C12  (Ca  Cl.)  roo8  „                               „  —  „ 

Mg  C12  (Mg.  Cl.)  3-479  „  0-189     „  0-769  „ 

Na2  SO4  (Na  O,SO3)  „  0-104     „  5-161  „ 

NaCl.  4743  „  0-478     „  9-582  „ 
Residue  found  on 

Evaporation  7-210  „  18-864      „ 

He  shows  that  only  a  portion  of  the  calcium  sulphate  in  boiler  incrustations 
contains  water  of  crystallisation.  In  boilers  which  have  been  submitted  to  a 
very  high  pressure  it  occurs  anhydrous.  Magnesia  exists  as  hydrate,  the 
magnesium  chloride  giving  up  its  hydrochloric  acid  under  the  influence  of 
heat.  The  magnesium  carbonate  is  decomposed  at  a  temperature  little  above 
100°,  and  magnesium  sulphate  undergoes  mutual  decomposition  with  calcium 
carbonate,  the  carbonic  acid  escaping.  From  a  number  of  analyses  given  it 
is  noticeable  that  the  higher  the  pressure,  and  consequently  the  higher  the 
temperature,  up  to  3  atmos.,  the  larger  the  quantity  of  2CaSO4:fH2O,  in 
comparison  with  the  CaCO3.  But,  contrary  to  the  opinions  of  many,  Fischer 
holds  that  carbonate  of  lime  suffices  of  itself,  or  probably  also  aided  by  silica, 
to  form  a  hard  crust. 

It  appears  from  analyses  of  marine  crusts  to  be  probable  also  that  the 
quantity  of  Na  Cl  in  the  crusts  increases  with  increase  of  the  steam  pressure 
under  which  these  have  been  formed. 

CORROSION. 

FROM  one  or  two  causes,  corrosion  has  been  found  to  attack  the  exterior 
surfaces  of  boilers,  and  eventually  to  work  considerable  damage.  This, 
however,  is  a  simple  matter,  as  the  action  in  these  cases  is  easily  preventable. 

Thus,  in  the  case  of  land  boilers,  careless  setting  in  too  much  lime  has  pro- 
duced bad  effects — the  part  of  the  boiler  shell  exposed  to  the  probably  impure 
lime  having  been  eaten  away  to  a  large  extent. 

Setting  the  boilers  upon  a  damp  foundation  without  proper  provision  for 

small  transparent  prisms  coloured  with  carbonaceous  matter.    (Johnson,  Phil.  Mag.  J.  13,  325 
Also  /.  pr.  Chem.  16,  100.) 

Calculation.  Johnson. 

2  Ca  O,  SO3  136.  93-79  93-272 

HO  9.  6-21  6-435 

Carb.  matter  0-293 


145  100-00  100-00 


APPENDIX.  615 

draining,  has  also  resulted  in  rapid  destruction,  whether  the  moisture  reached 
the  boilers  through  the  lime  of  the  setting  or  through  the  ashes. 

Both  marine  and  land  boilers  have  been  seriously  corroded  by  ashes,  when 
cold,  having  been  carelessly  allowed  to  remain  in  contact  with  the  iron.  The 
ashes  contain  a  considerable  quantity  of  alkaline  salts  of  some  strength  ;  and 
with  damp  drawn  from  the  bilge  water  in  vessels,  or  from  the  ground  ashore, 
or  by  deliquescence  from  the  atmosphere,  these  salts  have  been  enabled  to 
attack  the  iron  vigorously. 

It  has  also  been  found  by  S.  Dana  Hayes  (Client.  News,  vol.  xxx.,  153,  Jour. 
Client.  Soc.,  vol.  xiii.,  p.  294)  that  the  soot  in  tubes  and  flues  has  become 
charged  with  pyroligneous  acid,  where  wood  has  been  freely  used  in  lighting 
tires,  or  large  quantities  of  coal  have  been  charged  at  a  time  ;  and  that  this 
combination  has  caused  corrosion.  The  same  result  has  been  caused  by  soot 
retaining  fine  dust  of  ashes,  and  in  consequence  also  sulphur  acids,  derived 
from  pyrites  in  the  coal.  A  case  of  this  kind  is  also  published  by  J.  W. 
Chalmers  Harvey,  in  Chcm.  News,  xxxii,  252  ;  Client.  Soc.  Jour.,  No.  clxi., 
p.  796. 

It  is  sufficient,  however,  to  point  out  these  causes,  for  they  suggest  their 
own  remedies.  Care  in  preparing  and  completing  the  setting,  in  cleaning 
flues  and  ash  pits,  and  in  firing  being  all  that  is  necessary  to  prevent  corrosion 
from  them. 

The  injudicious  use  of  brass  cocks  and  connections  bolted  or  fastened 
directly  to  the  boiler  shell,  has  often  resulted  in  corrosion  from  galvanic 
action  at  the  places  where  the  two  metals  come  in  contact.  This  action 
proceeds  more  rapidly  when  a  little  leakage  of  water  takes  place  at  the  joint 
or  connection. 

The  operation  of  corroding  forces  in  the  interior  of  boilers  is,  however, 
far  more  serious  and  baffling.  Yet  even  these  forces  may  be  reduced  to 
submission,  but  they  demand  study  in  the  becoming  spirit  of  patient 
inquiry. 

Many  investigations  of  these  forces  and  their  actions  have  been  made,  and 
it  is  advisable  to  review  these  before  attempting  to  deal  with  the  subject  from 
an  engineering  point. 

One  of  the  first  to  publish  experiments  and  trials  connected  with  the 
corrosion  of  metals  was  the  late  Professor  Grace  Calvert,  who  exposed  iron  and 
steel  (with  other  metals)  to  the  action  of  sea-water,  of  natural  fresh  water,  and 
of  distilled  water,  with  and  without  air.  He  also  submitted  iron  and  steel  to 
the  action  of  various  gases,  with  and  without  moisture,  and  to  that  of  various 
acids.  In  general,  the  results  obtained  by  him  showed  that  steel  and  then 
iron  were  most  rapidly  corroded  by  sea-water  when  simply  immersed  in  the 
sea  for  a  time.  (105-31  grammes  of  steel  and  9930  of  iron  being  dissolved 
from  plates  of  forty  centimetres  square  by  immersion  in  the  sea  for  one 
month.)  Also  that  iron  immersed  in  water  containing  carbonic  acid  oxidised 
rapidly  with  escape  of  hydrogen  gas,  which  led  him  to  suppose  that  some 
galvanic  action  had  part  in  the  operation.  He  may,  however,  have  meant 
merely  thus  to  designate  the  decomposition  of  a  part  of  the  water  by 
which  oxygen  was  dissociated  and  combined  with  the  iron  under  the 
influence  of  the  carbonic  acid.  The  corrosive  action  of  carbonic  acid  was 
corroborated  by  his  experiments  with  gases,  for  when  bright  blades  of  steel 
and  iron  had  been  exposed  for  four  months  to  the  action  of  various  gases  he 
obtained  the  following  results  :  There  was  no  oxidation  with  dry  oxygen  ; 
with  damp  oxygen,  one  blade  only  out  of  three  experiments  was  slightly 
oxidised  ;  no  oxidation  with  dry  carbonic  acid  ;  with  damp  carbonic  acid 
there  was  a  formation  of  white  carbonate  of  iron  on  the  blades  ;  no  oxidation 
with  dry  carbonic  acid  and  oxygen,  but  very  rapid  oxidation  with  damp 
carbonic  acid  and  oxygen.  He  also  found  that  distilled  water  which  did  not 
contain  air  or  gases  was  without  corrosive  action  upon  iron,  a  bright  blade 


616  APPENDIX. 

which  was  immersed  in  such  water  having  become  in  some  days  merely  here 
and  there  spotted  with  rust.  It  was  found  that  at  these  spots  where  oxida- 
tion had  taken  place,  there  were  impurities  in  the  iron  which  had  induced 
galvanic  action,  "  just  as  a  mere  trace  of  zinc  placed  on  one  end  of  the  blade 
would  establish  a  voltaic  current." 

An  analagous  action  of  distilled  water  with  and  without  air  was  observed 
in  his  experiments  with  lead — 200  litres  of  distilled  water  without  air  having 
dissolved  during  eight  weeks  only  r829  gramme  from  a  surface  of  I  square 
metre,  while  the  same  quantity  of  distilled  water  when  aerated  dissolved  in 
the  same  time  110*003  grammes.1 

These  investigations  were  made  the  basis  of  an  inquiry  by  Mr.  W.  Kent, 
of  the  Stevens  Institute  of  Technology,  into  the  corrosion  of  iron  in  railway 
bridges  in  the  U.S.,  and  by  their  means  he  was  enabled  to  arrive  at  a  satis- 
factory demonstration  of  the  causes  of  the  action.  His  paper  was  published 
in  the  Engineer  in  Aug.,  1875. 

Recently,  some  of  Calvert's  results  have  been  verified  by  A.  Wagner,  who 
publishes  (in  Dingier' s  Polyt.  Jour.,  218.70-79)  an  important  paper  on  the 
Influence  of  Various  Solutions  on  the  Rusting  of  Iron.  Distilled  water  free 
from  air  does  not  appear  to  have  been  tested,  but  with  air  freed  chemically 
from  all  carbonic  acid,  a  slight  rusting  was  noticed,  the  water,  however,  soon 
becoming  saturated  with  its  proper  quantity  of  iron.  The  action  of  carbonic 
acid  (or  carbon  dioxide)  observed  by  Calvert  is  also  noted,  and  the  fact 
noticed  for  the  first  time  that  the  presence  of  chlorides  of  magnesium, 
ammonium,  sodium,  potassium,  barium,  and  calcium  in  the  water  largely  in- 
creases the  production  of  rust,  while  this  important  fact  also  appears  from 
his  results,  that  the  corrosive  action  of  all  these  substances  is  considerably 
increased  by  the  presence  of  air  and  carbonic  acid  in  solution.  Chloride  of 
magnesium  of  all  these  salts  is  the  most  active  agent  when  alone  in 
corroding  the  iron,  but  combinations  of  chloride  of  magnesium  and  carbonate 
of  lime,  of  chlorides  of  barium  and  calcium,  and  of  chlorides  of  sodium  and 
calcium  have  also  considerable  corrosive  action. 

This  to  some  extent  corresponds  with  the  fac^  observed  by  Mr.  John 
Gamgee,  as  a  difficulty  which  he  had  to  encounter  in  conneccion  with  the 
continuous  freezing  of  water  for  his  "  Glaciariiim,"  viz.,  that  the  brine  solu- 
tions used  as  media  of  congelation  act  destructively  upon  the  metallic 
surfaces  of  the  pipes  or  channels  through  which  they  are  conveyed. 
(Engineering,  vol.  xxi.,  page  226.) 

Wagner,  however,  has  also  noticed  that  while  chloride  of  magnesium  solution 
in  the  absence  of  air  attacked  iron  at  a  temperature  of  about  100°  Cent.,  the 
chlorides  of  sodium,  potassium,  barium,  and  calcium  were  without  action 
under  these  circumstances.  This  author  also  notices  the  fact,  the  observance 
of  which  is  ascribed  to  Mr.  Young,  of  Kelly  (in  a  paper  read  by  Mr.  James 
R.  Napier  before  the  Phil.  Society  of  Glasgow,  Dec.  i6th,  1874),  viz.,  that 
the  presence  of  an  alkali  in  water  protects  iron  and  prevents  rusting. 
In  consequence  of  the  great  importance  of  his  results,  I  give  two 
tables  of  figures  (from  the  four  contained  in  his  paper)  representing  some  of 
them- 

1  Sir  R.  Christison  has  made  investigations  into  the  action  of  water  on  lead  (Chemical 
News,  vol.  xxviii.  15),  but  seems  in  his  conclusions  not  to  have  distinguished  between  distilled 
water  and  pure  natural  waters,  merely  comparing  them  with  respect  to  purity.  Yet  the  fact 
that  he  always  found  carbonate  of  lead  formed  by  the  action  of  the  purest  waters  suggests  that 
the  action  was  due  to  the  presence  of  gases  in  solution,  and  not  to  the  water  itself. 


APPENDIX. 


617 


No. 

Solutions. 

Percentage  of  loss  of  weight  in  i  week. 

With  air  free  from  CO2. 

With  air  and  CO2. 

I. 

Freshly  distilled  water  ... 

0*83 

1'53 

2. 

Containing  Ba  C12  and  Ca  C19 

1*63 

l-46 

3- 

NaClandKCl      ... 

T20 

2-03 

4- 

MgCl2        

1-40 

1-85 

5- 

NH4  Cl       

1-29 

2-16 

6. 

K(OH)2       

— 

— 

7- 

NaCo,        

— 

— 

8. 

,,          Sea  water  ... 

T26 

I  -02 

9- 

„          Sea  water  evaporated 
and  oil  5  drops  ... 

0,7 

073 

No. 

Solutions. 

Boiling  in  contact  with  air  then  and  while  cooling. 

Percentage  of  loss  of  weight  in— 

i  week. 

2  wks. 

3  wks. 

4  wks. 

5  \vks. 

6  wks. 

,. 

Distilled  water          

0-44 

0.82 

ri5 

i  '53 

2'02 

2-46 

2. 

Flask  half-filled  with  distilled 

water  —  i.e.,  more  air 

roi 

1-62 

275 

3-68 

4'53 

5-l8 

3- 

Containing  Ba  C12  and  CaCl2 

0-66 

1-33 

I'57 

1-82 

2-03 

2-27 

4- 

NaClandKCl... 

0-84 

i  "47 

2-15 

2'57 

3'04 

3'4I 

5- 

MgCl2  

1-31 

1-91 

2'20 

2-4.) 

276 

3'05 

6. 

,,           MgCl2  and  excess 
of  Ca  CO3     ... 

0-89 

i  '54 

2-08 

2-46 

2-97 

3-27 

7- 

NH4C1  

i*i5 

r86 

2-56 

3"i6 

366 

4'I6 

8. 

K(OH)2  

__ 

— 

— 

— 

— 

— 

9- 

Na  CO3  

— 

— 

— 

— 

— 

— 

10. 

Sea-  water 

o-43 

°'°5 

O7O 

075 

0-97 

1-24 

n. 

Sea-water  and  Ba  C12 

0-15 

0-46 

0-69 

0-92 

ro8 

T23 

12. 

Sea-water  and  10  drops  oil 

Q'59 

0'59 

0'62 

072 

0-83 

0'93 

618  APPENDIX. 

I  quote  here  an  important  experiment  made  by  him  on  the  effect  of 
chloride  of  magnesium  on  iron  at  boiling  temperature. 

Two  grammes  of  neutral  magnesic  chloride  were  introduced  into  a  strong 
tube,  in  which  weighed  pieces  of  iron  were  placed  ;  boiling  distilled  water 
was  added,  and  the  tube  sealed  up  while  steam  was  issuing.  It  was  then 
kept  at  100°  Cent.  (212°  F.)  for  six  weeks,  and  after  cooling  was  opened. 
Gas  was  evolved  on  opening  it  ;  the  iron  was  black,  and  had  lost  0-39  per 
cent,  in  weight,  and  the  solution,  when  filtered,  contained  chloride  of  iron 
(ferrous  chloride).  (Dinglcr's  P.  /.,  ccxviii.  70-79.  Chem.  Soc.  7.,  No.  clx. 
p.  522.) 

Still  another  valuable  contribution  to  our  knowledge  of  this  subject  comes 
to  us  from  Germany,  in  the  results  of  an  examination  of  the  effects  of  con- 
densed water  containing  grease  on  boilers  which  were  fed  with  it,  by  Stingl, 
an  author  who  also  proposed  and  successfully  carried  out  a  method  for  the 
purification  of  that  wrater. 

The  water  was  evidently  condensed  by  means  of  an  injection  condenser,  as 
salts  of  lime  and  magnesia  were  present  in  small  quantity  in  the  condensed 
water.  These  salts,  in  presence  of  grease,  at  a  temperature  not  exceeding 
60°  to  70°  C.,  form  lime-soap — part  of  the  lime-salts  being,  as  has  already 
been  shown,  rendered  insoluble  at  these  temperatures.  The  lime-scap, 
under  the  influence  of  a  higher  temperature,  partially  decomposes  into  free 
fatty  acid  and  an  organic  substance  which  is  reducible  by  further  heat, 
yielding  a  carbonaceous  residue.  This  substance  is  a  kind  of  basic  lime-soap 
which  adheres  to  the  boiler  surfaces,  while  the  acid,  which  is  usually  oleic 
acid,  attacks  and  dissolves  the  iron.  In  the  crust  the  fatty  acid  is  recog- 
nised by  the  addition  of  hydrochloric  acid,  the  separated  organic  mass 
being  afterwards  shaken  with  ether.  The  boiler  crusts  have  usually 
a  dark  colour,  partially  due  to  the  presence  of  oxide  of  iron,  partly  to 
separation  of  carbon  from  the  fatty  acid  partially  decomposed.  Even  if 
lime  and  magnesia  salts  are  present  in  very  insignificant  proportion,  the 
presence  of  grease  is  none  the  less  injurious,  as  with  saponification 
under  great  pressure,  a  very  small  quantity  of  lime  suffices  to  occasion 
the  splitting  up  of  a  neutral  fat  into  free  fatty  acid  and  glycerine  ;  with 
low  pressure  it  is  not  doubted  that  the  same  decomposition  occurs,  though 
more  gradually. 

A  sample  of  very  soft  water  (6C  of  hardness)  depositing  very  little  crust  was 
submitted  to  the  author  of  that  paper,  as  a  boiler  in  which  it  had  been  used 
was  completely  destroyed  after  three  years'  work.  This  water  had  a  milky 
appearance,  and  contained  0*212  part  of  fat  in  one  litre. 

He  also  quotes  the  case  of  the  corrosion  of  a  gasometer,  the  cistern  of 
which  had  been  luted  with  greasy  condensation  water.  The  gasometer 
would  have  lasted  20  or  30  years  had  ordinary  water  been  used,  but  in  the 
circumstances  mentioned,  that  part  of  it  exposed  to  the  water  was  corroded 
through  after  four  years. 

The  destructive  action  of  the  oleic  acid  on  the  oil-pumps  used  in  stearin 
candle  manufactories  is  also  alluded  to.  And  the  following  details  are  given 
of  an  interesting  case  of  boiler  corrosion,  with  accompanying  incrustation, 
and  of  the  means  used  to  overcome  the  destructive  action.  The  condensed 
water  from  two  steam  engines,  respectively  of  300  and  100  horse-power,  was 
used  to  feed  a  steel  boiler  of  the  Cornish  design.  After  only,  three  weeks' 
firing,  water  began  to  leak  into  the  tubes,  and  shortly  after  the  boiler  had  to 
be  stopped  for  examination  and  repair.  A  deposit  on  the  upper  part  of  the 
tubes,  from  8  to  n  mm.  thick,  was  found.  The  water  had  an  opalescent 
appearance,  at  once  removed  by  ether,  which  the  author  recommends  as  a 
good  qualitative  test  for  the  presence  of  grease  in  water.  The  following  is 
the  result  of  analysis  of  the  condensed  water,  which  was  obtained  at  a 
temperature  of  40°  to  50°. 


APPENDIX. 


619 


Calcium  carbonate     ... 
Magnesium  carbonate 
Calcium  sulphate 
Magnesium  chloride  ... 
Sodium  chloride 
Ferric  oxide  and  alumina 
Silica 
Organic  matter 

Total 


In  10,000  parts. 

..  1-3091 

. .  0*6930 

-.  0-3158 

..  0-0134 

..  0'1200 

..  0-0241 

..  0-0023 

...  0-4138 


2-8915 


The  crust  deposited  from  this  water  had  a  dark  greyish-brown  colour  and 
was  friable  ;  but  w,hen  pulverised  it  was  difficult  to  wet  with  water.  It 
effervesced  strongly  with  hydrochloric  acid,  a  black  fatty  mass  being  left 
floating  on  the  surface  of  the  acid,  which,  shaken  with  ether,  yielded  thereto 
about  5-19  per  cent,  of  a  brown  oil.  The  residue,  insoluble  in  hydrochloric 
acid,  was  washed  with  ether  to  remove  fat,  dried  at  100  deg.,  weighed  and 
ignited.  The  following  shows  the  full  analysis  : — 


Calcium  carbonate 
Magnesium  carbonate 
Magnesium  hydrate 
Calcium  sulphate 
Ferric  oxide    ... 
Alumina 
Silica 
Fat  acids 
Combustible  matter 


51-42  per  cent. 
11-30 

3-90 

6-63 
12-75 

0-31 

0'34 

5'i9 

8-46 


100-30 


In  order  to  purify  the  water,  the  calcium  carbonate  and  part  of  the 
magnesium  carbonate,  with  all  the  grease,  were  removed  by  precipitation  and 
subsequent  filtering.  The  fat  particles  were  removed  by  being  enveloped  by 
the  precipitated  calcium  carbonate,  which  mechanically  retained  them  on  the 
filter,  the  reaction  being  favoured  by  suitable  temperature  and  intimate 
mixture  previous  to  filtering. 


The  water  then  contained  in 

Calcium  carbonate 
Magnesium  carbonate 
Calcium  sulphate 
Magnesium  chloride 
Sodium  chloride 
Silica    ... 

Ferric  oxide  and  alumina 
Organic  matter  ... 


Total 


...  10,000  parts. 

...  0-1773 

...  0-4135 

...  0-2068 

...  0-0108 

...  0-2351 

...  traces. 

...  traces. 

...  0-1512      „ 

...  1-1947  Parts. 


No  grease  could  be  detected  in  the  filtered  water,  which  was  then  used  in 
the  same  boiler,  after  being  repaired,  for  three  months,  when  the  deposit  on 
the  tubes  was  found  to  amount  to  a  layer  of  only  the  thickness  of  a  sheet  of 
paper  and  almost  wholly  consisted  of  gypsum,  and  easy  to  remove.  The 


620  APPENDIX. 

whole  amounted  to  only  5  kilos,  in  weight  after  3  months'  steady  work, 
was  a  loose  greyish-brown  mass,  the  following  showing  the  analysis  : — 

Calcium  carbonate         ...  ...  ...  ...  19-30  per  cent. 

Magnesium  carbonate  ...  ...  ...  ...       1-26 

Magnesium  hydrate      ...  ...  ...  ...  45^02 

Calcium  sulphate  ...  ...  ...  ...  15-12 

Ferric  oxide    ...  ...  ...  ...  ...       9-43 

Silica  ...  ...  ...  ...  ...       2'O4 

Organic  matter  (insol.  in  ether) ...  ...  ...       7-35 

Fatty  matter  ...  ...  ...  ...  traces. 


To  purify  such  water  as  the  above  named  for  high  pressure  boilers,  'a 
mixture  of  lime-water  and  caustic  soda  solution  is  recommended,  as  this  not 
only  removes  fat  acids  but  also  removes  the  magnesia,  which  forms,  with 
gypsum,  hard  incrustations  at  high  temperatures.  (Dingier  Polyt.,  /.,  ccxv., 
115-121  ;  Chew.  Soc.  /.,  vol.  xiv.,  sec.  2  p.  132.) 

In  a  letter  on  the  corrosion  of  boilers,  addressed  by  me  in  October,  1874,  to 
the  Editor  of  Engineering  (and  published  in  that  paper  on  October  23,  1874), 
reference  was  made  to  the  Report  on  Corrosion  of  the  Tubing  of  two  of 
Rowan  and  Horton's  Patent  Boilers,  by  Mr.  Thomas  Spencer,  an  analytical 
chemist.  Starting  from  the  slender  basis  afforded  by  the  examination  of 
water  mains  in  two  cases  of  internal  corrosion  of  these,  where  a  very  pure 
natural  water  was  conveyed  through  them,  Mr.  Spencer  argued  that  the 
corrosion  in  these  boilers  was  due  to-the  use  of  distilled  water,  which  alone 
was  used  in  them,  but  which  he  confounded  with  pure  natural  water.  In  the 
absence  of  any  well  ascertained  facts  as  to  boiler  corrosion,  his  opinion  was 
accepted  as  sufficiently  explanatory  of  the  action  ;  but,  as  is  often  the  case 
with  half-knowledge,  that  which  was  true  in  his  investigations  was  rendered 
indistinct  by  crude  conjectures.  In  consequence  of  this,  in  the  letter  referred 
to,  and  generally  in  all  published  opinions  emanating  from  engineering 
sources  which  I  have  seen,  neither  the  great  difference  between  genuine 
distilled  water  and  pure  natural  waters — viz.,  the  quantity  of  air  and  gas 
which  is  invariably  held  by  the  latter — has  been  properly  weighed  or  even 
acknowledged,  nor  has  the  only  point  of  similarity  between  the  distilled 
water  from  surface  condensers  known  on  board  steamers  and  pure  fresh 
water — viz.,  that  there  is  always  some  air  present  in  the  former — been  noticed 
or  allowed  for.  In  the  letter  referred  to,  I  regret  that  I  also  confounded 
distilled  water  with  Loch  Katrine  water,  through  having  in  view  merely 
purity,  and  not  considering  the  presence  of  air  or  gases. 

In  considering  now  some  examples  of  boiler  corrosion,  I  shall  adopt  the 
arrangement  already  used  in  the  section  on  Incrustation,  viz.  : — 

1.  Land  boilers  using  natural  fresh  waters  ;  and, 

2.  Marine  boilers. 

i.  From  what  has  been  before  us  in  connection  with  Incrustation,  it  is 
plain  that  it  is  only  in  those  land  boilers  which  are  fed  with  pure  natural 
waters  that  we  are  likely  to  find  Corrosion  at  work.  Where  lime  salts  are 
present,  a  crust  is  formed,  and  the  metal  surfaces  of  the  interior  of  the  boiler 
are  thus  kept  from  contact  with  the  water  and  any  corroding  ingredient  in  it. 
The  special  inconveniences  of  such  crust  formation  we  have  already  consi- 
dered. Highly  chalybeate  waters,  although  not  depositing  a  crust,  do  not 
seem  to  act  injuriously.  A  case  is  mentioned  in  Mr.  James  Napier's  paper  in 
Proc.  Phil.  Soc.  G.,  demonstrating  this.  There  may,  however,  be  some 
material  forming  part  of  the  crust,  or  adhering  to  it,  which  suffers  decompo- 
sition in  contact  with  the  heated  iron,  and,  as  a  consequence,  attacks  the 


APPENDIX.  621 

metal.  This  is  the  case  with  crusts  formed  with  fat  or  greasy  substances,  as 
in  the  instance  already  quoted  in  the  paper  by  Stingl. 

We  have,  in  this  district,  ample  opportunity  of  proving  the  effect  of  very 
pure  fresh  water  upon  boilers,  because  there  are  few  natural  waters  of 
greater  purity  than  that  from  Loch  Katrine,  with  which  various  manufactories 
in  and  around  this  city  are  supplied. 

The  water  formerly  supplied  to  Glasgow  having  been  calcareous,  it  has 
been  found  that  boilers  which  used  it  for  some  time  have  not  suffered  from 
corrosion  when  subsequently  fed  with  Loch  Katrine  water — the  explanation 
of  this  being  the  fact  that  the  thin  coating  of  lime  which  these  boilers  had 
acquired  acted  as  an  efficient  and  permanent  protection. 

Where,  however,  owners  or  managers  have  been  very  zealous  in  removing 
by  mechanical  or  chemical  means  every  trace  of  that  crust  in  order  to  get  the 
full  benefit,  as  they  have  thought,  of  the  pure  water,  the  result  has  been 
different  and  the  "  full  benefit "  has  often  been  of  a  kind  to  perplex  them.  When 
also  new  boilers  have  been  started  from  the  first  with  Loch  Katrine  water, 
corrosion  has  been  more  or  less  rapid,  and  considerable  trouble  and  incon- 
venience have  been  caused  thereby. 

These  facts  find  illustration  in  many  manufacturing  establishments  around. 
I  have  been  informed,  amongst  others,  of  a  boiler  attached  to  a  mill  in 
Bridgeton,  where  every  care  was  taken  to  remove  all  scale  before  introducing 
Loch  Katrine  water,  and  the  millowners  were  chagrined  by  finding  their 
boiler  quickly  suffer  from  corrosion. 

In  an  engineering  work  at  Port  Dundas,  one  boiler  which  had  wrought 
upon  a  supply  of  the  former  calcareous  water,  and  was  latterly  supplied  with 
Loch  Katrine  without  being  scaled,  continued  to  work  for  some  years  with- 
out showing  symptoms  of  distress  from  corrosion.  In  the  same  works, 
however,  a  range  of  new  boilers,  put  down  after  the  introduction  of  the  pure 
water,  suffered  so  severely  as  to  require  constant  repairs  at  tubes,  and  an 
entire  new  set  of  tubes  (of  between  40  and  50  in  each  boiler)  in  a  compara- 
tively short  time.  In  another  engineering  work  on  the  south  side  of  the  city, 
the  main  shop  boiler  was  worked  for  three  or  four  years  without  suffering 
corrosion  with  Loch  Katrine  water,  after  having  worked  previously  for  seven 
or  eight  years  with  the  former  Glasgow  water.  When  a  new  boiler  was 
substituted  for  this  old  one,  although  the  new  one  was  subjected  to  precisely 
the  same  conditions  as  those  its  predecessors  wrought  under  for  some  years 
without  trouble  or  difficulty,  it  was  found  to  the  consternation  of  the  pro- 
prietors that  the  new  boiler  was  corroding  away  so  fast  as  to  suggest  that  a 
third  boiler  would  be  required  very  soon.  Until  the  presence  and  effect  of 
the  lime  coating  in  the  former  boiler  were  pointed  out,  it  was  impossible  for 
them  to  understand  how  one  boiler  should  be  able  to  use  Loch  Katrine  water 
without  damage,  while  another  similarly  worked  should  suffer  in  so  short  a 
time. 

In  the  former  of  these  two  examples  no  condensed  water  was  fed  into 
the  boilers,  as  'they  were  working  in  connection  with  high  pressure  atmos- 
pheric engines  and  other  machines  ;  consequently  there  was  no  grease  or 
other  corrosive  agent  introduced  into  them,  and  thus  the  corrosion  could  be 
traced  directly  to  the  water.  In  the  latter  one,  a  part  of  the  condensed 
steam  was  collected  in  the  feed  cistern,  and  a  considerable  quantity  of  grease 
thus  found  its  way  into  the  boiler,  thus  aiding  the  corrosion  somewhat. 
Steps  were  at  first  taken  to  exclude  this  grease  from  the  boiler,  but  the 
corrosion  afterwards  proceeded — large  quantities  of  oxide  of  iron  being 
removed  from  the  boiler — until  means  were  adopted  to  overcome  the 
action. 

The  following  is  the  result  of  the  analysis  of  the  water  made  during  July, 
and  published  by  Professor  Mills,  who  informs  me  that  it  represents  a  fair 
average  of  the  quality  of  the  Loch  Katrine  supply . 


622  APPENDIX. 

In  100,000  parts. 

Total  solid  impurity       ...             ...  ...  ...  3-16 

Organic  Carbon              ...             ...  ...  ...  O'lio 

Organic  Nitrogen           ...             ...  ...  ...  0-033 

Ammonia 

Nitrogen  as  nitrates  and  nitrites  ... 

Total  combined  Nitrogen              ...  ...  ...  0^033 

Chlorine           ...             ...             ...  ...  ...  070 

Hardness          ...             ...             ...  ...  ...  0-48 

The  report  also  bears  that  the  water  \vas  pale  brown  in  colour  and  con- 
tained traces  of  fibrous  matter  and  muddy  particles,  and  that  the  general 
condition  was  very  satisfactory. 

Nothing  contained  in  the  water  as  impurity  can  account  for  its  destructive 
action  ;  but  the  fact  that  it  contains  7  to  8  cubic  inches  of  gas  (of  which 
about  3  cubic  inches  are  oxygen)  to  the  gallon  in  solution,  coupled  with  the 
investigations  already  quoted  in  this  paper,  as  to  the  effect  of  distilled  water 
without  gas  and  of  water  containing  gas,  makes  all  plain.  The  corrosion  is 
due  to  the  action  of  the  carbonic  acid  and  oxygen  held  by  the  water,  and  the 
action  is  all  the  more  rapid,  from  the  absence  from  the  water  of  any  mineral 
matter  with  which  the  gases  can  combine.  In  both  of  these  engineering 
works  an  artificial  coating  of  lime  was  formed  in  the  interior  of  the  boilers, 
by  feeding  regularly  into  them  each  morning  for  some  time  a  whitewash  of 
Irish  lime  and  water.  This  expedient  was  quite  successful  in  checking  the 
corrosive  action,  and  as  the  lime  soon  hardened,  under  the  influence  of  the 
heat,  no  trouble  was  experienced  in  preserving  the  coating.  Pieces  of  lime- 
stone were  also  placed  in  the  feed  tank  or  cistern,  but  it  is  doubtful  if  they 
produced  much  effect.  Where,  however,  it  is  possible  to  mix  with  Loch 
Katrine  or  other  pure  water,  a  proportion  of  a  calcareous  natural  water  for  a 
time,  the  scale  formed  thus  in  working  will  probably  be  of  a  more  enduring 
nature.  I  strongly  recommend  this  plan  to  those  using  Loch  Katrine  water 
who  have  access  to  former  sources  of  supply. 

2.  MARINE  BOILERS. — We  are  introduced  to  a  variety  of  corrosive  actions) 
in  considering  marine  boilers,  according  as  we  have  to  deal .  with  boilers 
working  with  nothing  but  fresh  water  or  those  which  use  a  proportion  of  sea- 
water.  It  is  necessary,  however,  clearly  to  distinguish  these  two  classes 

The  only  marine  boilers  as  yet  using  exclusively  fresh  water,  in  regular 
working,  with  which  I  am  acquainted  are  those  of  Rowan  £  Horton,  men- 
tioned in  the  letter  to  Engineering,1  to  which  I  have  referred,  and  elsewhere, 
and  those  working  on  Perkins'  plan.  Some  of  the  ordinary  boilers  used  in 
steamers  with  what  are  called  compound  engines,  have  been  occasionally 
wrought  entirely  with  fresh  water,  but  in  every  such  case  recorded,  that 
manner  of  working  was  abandoned  after  a  very  short  trial,  in  consequence  of 
the  rapid  corrosion  which  was  discovered  to  be  going  on.  Boilers  in 
vessels  whose  voyages  are  always  made  in  sea-water,  are  constantly  liable  to 
receive  a  small  quantity  of  salt  water  by  leakage  through  surface  condenser 
joints,  or  some  other  connections,  so  that  even  where  it  is  or  has  been  the 
intention  to  use  fresh  water  only,  it  is  not  possible  without  analysis  to  de- 
termine if  that  has  been  done.  The  first  of  the  examples  quoted  above  have, 
Jiowever,  this  element  of  uncertainty  removed  from  their  case  in  consequence 
of  their  steamers  running  in  fresh  water,  except  for  a  very  small  part  of 
their  voyage.  In  their  case  corrosion  from  fatty  acids  and  from  galvanic 
action,  of  what  may  be  called  an  intermittent  kind,  was  experienced  and 
successfully  counteracted.  These  actions,  and  the  respective  remedies 
which  were  adopted,  I  have  mentioned  in  the  published  letter  referred  to, 

1  This  letter  is  printed  at  the  end  of  this  paper. 


APPENDIX.  623 

and  I  quote  them  here  because  they  show  what  are  the  corrosive  forces  to 
which  marine  boilers,  working  exclusively  with  fresh  water,  may  be  sub- 
jected. Lime  was  present  in  small  quantity  in  the  river  water  used  to  fill  up 
the  boilers  at  starting  and  to  make  up  waste  in  working,  so  that  the  de- 
composition" of  fats  already  described  could  take  place.  When  the  grease 
was  removed  as  much  as  possible  by  filtering  the  feed  water,  and  the  pre- 
sence of  any  free  acid  was  neutralised  by  zinc,  the  corrosion  ceased.  The 
galvanic  action  was  also  arrested  by  means  of  the  filter,  because  in  general 
tliis  action  was  caused  by  local  contact  with  particles  of  metal  carried  into  the 
boiler,  and  not,  as  has  been  erroneously  supposed,  by  means  of  the  surface 
condenser  and  the  boiler  forming  together  the  two  elements  of  a  huge 
battery,  the  steam  and  water  being  the  exciting  medium. 

Of  Perkins'  boilers  worked  in  steamers  we  have  no  published  accounts 
with  which  I  am  acquainted,  so  that  we  cannot  say  whether  they  have 
suffered  from  corrosion  in  the  course  of  the  exigencies  of  practical  voyage 
making.  It  is,  I  know,  the  aim  of  Mr.  Perkins  to  exclude,  if  possible,  all  sea- 
water  and  all  oily  matter  from  his  boilers,  and  if  successful  in  doing  this, 
and  working  only  with  fresh  water,  the  corrosion  will  not  be  great.  Still, 
there  will  be  some,  as  the  gases  of  the  natural  fresh  water  with  which  the 
boilers  are  filled  at  starting  will  oxidise  their  proportion  of  iron,  and  in  the 
feed  water,  which,  as  condensed  steam,  has  been  returned  from  engines 
through  the  surface  condenser  and  discharged  by  the  air  pump  into  the  hot 
well,  there  is  of  necessity  (probably  not  much),  yet  some  air  present,  as  the 
condensation  takes  place  in  contact  with  air  ;  and  this  air  will  also  do  its  own 
share  in  corroding  fresh  portions  of  the  clean  surface  of  the  boilers.  It  is 
probable  that  if  these  boilers  are  introduced  into  merchant  steamers  and 
become  subject  to  the  invariable  emergencies  of  regular  trading,  by  which 
leakages,  deficient  supply,  and  contamination  of  feed  water  are  experienced, 
and  foreign  substances  find  their  way  into  the  boilers,  the  evils  of  corrosion 
may  be  known  to  a  greater  extent  than  that  to  which  they  reach  where  it  is 
possible  to  observe  all  the  precautions  of  the  inventor  of  that  system. 

Generating  steam  from  fresh  water  alone  is  undoubtedly  the  proper,  as  it  is 
sure  on  this  account  to  be  ultimately  the  general,  mode  of  operation  with 
steam  boilers,  but  for  ordinary  sea-going  purposes,  appliances  must  not  be  too 
delicate,  but  require  to  possess  the  power  to  endure  abnormal  and  adverse 
conditions. 

The  case  of  a  coasting  steamer  using  in  her  boilers  natural  fresh  water 
from  two  sources  (one  at  each  end  of  her  voyage)  whose  boilers  were  de- 
stroyed by  corrosion  with  great  rapidity,  was  made  known  by  Mr.  James 
Ciilchrist,  in  a  paper  read  before  the  graduate  section  of  the  Inst.  of  Engineers 
in  Scotland,  and  published  in  February  of  this  year  in  a  periodical  called 
Mtirhic  Kii^i'iurring  AYsc'.s.  Analyses  of  one  of  these  waters  (the  other  having 
been  Loch  Katrine)  and  of  the  deposit  found  in  the  boilers  are  given  in  the 
paper,  with  the  opinions  of  two  professional  chemists,  who  ascribed  the  corro- 
sive action  to  the  injudicious  use  of  a  large  quantity  of  tallow  in  engines  and 
boilers.  There  is  no  doubt  that  the  decomposition  of  the  tallow  was  in 
i  self  sufficient  to  cause  serious  damage  to  the  boilers  in  presence  of  fresh 
water  containing  a  small  quantity  of  lime  ;  but  the  action  in  this  case  was 
modified  by  a  fact  not  noticed  by  the  chemists  -AM/.,  that  during  the  voyage  of 
the  steamer  all  deficiency  in  feed  water  was  made  up  from  the  sea.  The  boiler 
deposit  consequently  contains  9-11  per  cent,  of  magnesia,  and  '12  per  cent,  of 
common  salt,  as  well  as  <X-,X6  per  cent,  of  oil  and  organic  matter  ;  and  it  is  to 
the  presence  and  decomposition  of  chloride  of  magnesium  to  which  the 
presence  of  magnesia  in  the  deposit  bears  witness,  as  well  as  to  the  carbonic 
acid  of  the  original  boiler  supply,  that  a  great  part,  and  probably  the  rapidity, 
of  the  corrosive  action  is,  I  believe,  to  be  attributed. 

This  leads  to   the  consideration   of  marine  boilers  using  partly  fresh  and 


624  APPENDIX. 

partly  salt  water,  by  far  the  most  extensive  class  at  present,  and  that  which 
has  suffered  most  from  corrosive  action. 

A  very  intelligent  account  of  the  state  of  matters  in  this  class  of  boilers  is 
given  by  Mr.  Milln,  in  a  paper  read  before  the  Cleveland  Iron  Trade  Fore- 
men's Association,  Nov.,  1875,  and  published  widely  in  the  engineering 
periodicals.  This  author  describes  graphically  the  introduction  of  the  surface 
condenser  into  marine  engine  practice,  with  which  is  coincident  the  com- 
mencement of  all  real  trouble  from  corrosion,  and  he  then  describes  the 
course  of  events  with  two  distinct  sets  of  marine  boilers.  In  the  first  of 
these  we  have  a  good  example  of  boilers  which  had  been  worked  at  com- 
paratively low  pressure  viz.,  25  Ibs.  per  square  inch  and  fed  for  four  years 
with  sea-water — working  during  that  time  in  connection  with  an  ordinary 
injection  condenser  attached  to  engines  which  indicated  900  horse-power. 
As  the  voyage  was  not  of  long  duration  and  time  was  given  for  regular 
"  scaling  "  of  the  boiler  surfaces  (i.e.,  removing  the  scale  from  them)  at  the 
close  of  every  voyage,  no  damage  was  done  by  incrustation  and  no  incon- 
venience beyond  the  cost  of  fuel  consumed  was  experienced.  The  injection 
condenser  was  then  replaced  by  a  surface  condenser,  some  of  the  old  incrus- 
tation being  left  adhering  to  the  boiler  surfaces,  and  the  boilers  were  worked 
for  some  time  thereafter  with  fresh  water,  the  deficiency  in  feed  supply 
being  made  up  from  the  sea.  The  crust  was  soon  removed  and  the  boilers 
corroded,  showing  pits  and  blotches  and  all  the  usual  symptoms. 

The  other  instance  quoted  by  Mr.  Milln  is  that  of  a  new  set  of  boilers 
working  at  65  Ibs.  pressure  in  connection  with  compound  engines  of  1700 
horse-power  and  surface  condenser,  evidently  an  excellent  example  of  average 
modern  steamship  machinery.  These  boilers  were  worked  from  the  first 
with  fresh  water,  the  waste  being  supplied  by  distilled  water,  yet  the  density 
of  the  water  increased  daily  and  corrosion  proceeded  at  the  same  time  most 
energetically.  After  one  voyage  the  boilers  were  filled  at  starting  with  sea 
water,  but  no  more  sea-water  was  added  during  the  voyage  except  the  small 
quantity  necessary  for  surplus  feed  supply.  Under  these  fresh  circumstances 
corrosion  still  proceeded,  though  it  was  thought  more  slowly,  and  was  only 
finally  stopped  by  what  is  called  "  changing  the  water,"  i.e.,  blowing  off  a 
quantity  regularly  and  replacing  it  with  sea-water,  thus  introducing  fresh 
quantities  of  sea-water  into  the  boilers  during  the  voyage. 

This  author  then  alludes  to  the  many  theories  explanatory  of  corrosive 
action  which  have  been  started,  but  only  to  reject  them  all  and  adopt  the 
popular  error,  that  corrosion  is  due  to  a  change  supposed  to  be  wrought  upon 
the  water  itself  by  distillation  or  re-distillation,  which,  according,  to  some, 
confers  upon  it  the  properties  of  a  powerful  solvent  of  metals,  and  according 
to  others,  although  they  do  not  like  to  state  it  thus  plainly,  this  distillation 
decomposes  the  water  and  dissociates  its  oxygen,  which  forthwith  attacks  the 
iron  of  the  boilers,  or  as  Mr.  Milln  puts  it :  "  the  constituent  elements  of  water 
when  frequently  re-distilled  undergo  such  a  change  as  to  greatly  intensify  its 
action  on  or  affinity  for  iron."  One  engineering  journal  indeed  very  confi- 
dently affirms  that  it  is  "  a  fact  but  too  familiar  to  engineers  that  the  con- 
tinuous boiling  of  distilled  water  in  an  iron  vessel  causes  the  destruction 
of  that  vessel,"  but  has  to  admit  that  the  circumstance  that  that  water  also 
passes  over  a  very  great  surface  of  brass  or  copper  (of  the  destruction  of 
which,  however,  not  a  word  is  said)  complicates  the  aspect  of  the  phenomena. 

It  must,  however,  be  confessed  by  engineers,  that  of  the  data  or  investiga- 
tions by  which  so  apparently  wild  a  theory  has  been  established  as  a  fact 
they  are  as  yet  profoundly  ignorant,  and  as  Mr.  Milln  observes,  "  it  is  with 
regard  to  the  nature  of  this  change  that  we  so  much  want  information  ! " 
There  is  this  solitary  fact  known  and  harped  upon,  viz.,  that  dry  steam  in 
contact  for  a  period  of  time  with  iron  or  carbon,  in  a  tolerably  fine  state  of 
division  and  at  a  red  heat,  is  decomposed,  hydrogen  gas  escaping,  while  the 


APPENDIX.  625 

oxygen  combines  with  the  iron  or  carbon.  But  this  has  never  been 
attempted  with  water  nor  can  it  be  done  with  steam  below  red  heat.  What 
is  known  of  the  action  of  distilled  water  proves,  indeed,  the  clean  contrary  to 
this  theory,  and  in  illustration  of  "  what  is  known,"  I  refer  to  those  investiga- 
tions which  I  have  already  quoted.  They  prove  that  it  is  the  presence  of  air 
or  gases  which  makes  the  difference  in  the  action  of  various  pure  waters,  and 
even  in  that  of  the  various  salts  dissolved  in  impure  waters,  and  that  when 
water  is  distilled  free  from  air,  its  corroding  power  is  lost.  Thus  the  remedy 
for  corrosion  proposed  by  some  engineers  to-day,  viz.,  that  the  condensed 
steam  should  be  aerated,  proves  to  be  a  foolish  suggestion,  for  this  would  but 
increase  the  power  of  that  water  to  corrode  the  iron  of  the  boilers. 

I  shall  be  within  the  strict  truth  when  I  say  that  it  is  hasty  to  conclude, 
from  examples  of  boiler  corrosion,  that  distilled  water  has  to  do  with  the 
corrosion,  for  the  fact  is  that  there  is  no  case  known  in  which  the  proper 
effects  due  to  the  employment  of  distilled  water  alone,  and  free  from  gases, 
upon  the  metal  of  boilers,  could  have  been  observed.  The  boilers  of  Rowan 
and  Horton,  and  of  Perkins,  present  the  nearest  approach  to  the  conditions 
requisite  for  such  information,  but  not  all  the  necessary  conditions  are  found 
even  in  these  instances.  The  examples  just  quoted  from  Mr.  Milln's  paper 
are  of  the  kind  with  which  engineers  are  more  generally  familiar,  and 
they  do  not  give  such  data  as  would  lead  to  the  conclusion  about  distilled 
water.  The  opinion  is  therefore  due  to  a  hasty  conclusion,  drawn  from 
the  coincident  occurrence  of  corrosion  with  the  introduction  of  surface 
condensers. 

In  the  first  example,  genuine  distilled  water  was  never  present.  The 
boilers  were  filled  up  with  fresh  water  at  starting  with  the  surface  condensers, 
but  not  only  was  waste  and  deficiency  of  feed  made  up  from  the  sea  during 
the  voyages,  but  there  was  also  the  saline  crust  adhering  to  the  boilers  to  be 
dissolved  or  partially  dissolved  by  the  fresh  water.  Contrary  to  the  opinion 
of  Mr.  Milln  and  others,  I  maintain  that  just  because  analysis  shows  that 
such  crust  contains  chloride  of  sodium  (in  appreciable  quantity  when  formed 
at  such  a  pressure  as  that  of  the  boiler  mentioned — viz.,  25  Ibs.  per  square 
inch),  if  not  also  other  soluble  ingredients,  a  certain  part  of  the  crust  must 
have  been — and  in  such  cases  always  is — dissolved  ;  and  thus  the  crust  is 
partially  disintegrated,  and  the  insoluble  magnesia  and  sulphate  of  lime  fall 
in  flakes  to  the  bottom  of  the  boiler.  The  fact  that  the  water  did  not  long 
remain  fresh  does  not  in  any  way  interfere  with  this  opinion,  for  it  is  a  fact 
well  known  that  salts  dissolve  more  readily  in  a  solution  of  other  salts  than 
in  fresh  water.  Hence  the  scale  would  come  off  even  more  rapidly  when  a 
small  quantity  of  sea-water  was  used. 

The  second  example  started  with  boilers  filled  with  natural  fresh  water, 
which  itself  has  (as  we  have  seen),  if  pure,  power  to  corrode  by  its  gases  in 
solution  ;  but  although  distilled  and  not  sea-water  in  this  case  was  used  for 
surplus  feed  supply,  the  salinometer  test  showed  plainly  that  pure  distilled 
water  was  never  present,  and  that  either  sea-water  was  getting  in  through  a 
leaky  condenser,  or  that  fatty  and  other  matters  were  accumulating  in  the 
boiler,  the  colour  and  taste  of  the  water  being  decided  indications  that  such 
(and  probably  both  of  these)  results  were  happening.  After  the  first  voyage 
which  gave  such  results,  sea-water  was  regularly  used  in  greater  or  less 
proportion. 

Thus  we  must  search  for  the  corroding  agents  apart  from  the  distilled 
water.  The  analyses  by  Dr.  Wallace  and  others,  of  boiler  crusts,  and  the 
researches  of  Wagner  and  Fischer  quoted  herein,  reveal  one  very  important 
one,  viz.,  the  chlorine  or  hydrochloric  acid  set  free  by  decomposition  of  the 
chloride  of  magnesium  in  the  sea-water.  This  decomposition  may  take 
place  under  the  influence  of  high  temperature  alone,  when  magnesium 
hydrate  is  deposited,  while  the  iron  is  attacked  by  the  hydrochloric  acid,  first 


626  APPENDIX. 

chloride  and  subsequently  oxide  being  formed.  As  the  combined  influences 
of  temperature  and  carbonate  of  lime  are  present,  it  is  probable  that  the 
sulphate  of  magnesia  is  also  decomposed,  and  that  some  oxychloride  of 
magnesia  is  also  formed,  but  this  has  not  yet  been  demonstrated  by  analyses 
of  deposits,  though  it  is  the  opinion  of  Dr.  Mills  and  others  that  part  of  the 
magnesia  reported  in  ordinary  analysis  of  boiler  deposits  from  sea-water 
exists  in  that  form.  Dr.  Fischer  also  demonstrates  that  this  mutual  decom- 
position of  magnesium  sulphate  with  calcium  carbonate  is  a  fact,  and  that  the 
liberation  of  carbonic  acid  also  necessarily  takes  place. 

The  researches  of  J.  Y.  Buchanan  "  on  the  power  of  sea-water  to  absorb 
carbonic  acid,"  to  which  I  have  already  referred,  have  shown  us  that  sea- 
water,  on  account  of  the  sulphates  which  it  holds  in  solution,  absorbs  a  large 
amount  of  that  gas,  which  it  readily  gives  up  on  the  sulphates  being 
decomposed  or  separated  from  the  wrater.  Such  decomposition  and  precipita- 
tion of  sulphates  occur  in  marine  boilers,  besides  there  being,  now  since  the 
surface  condenser  era,  repeated  boiling  of  the  water,  which  of  itself  in  time 
liberates  nearly  all  the  carbonic  acid.  We  have  in  these  two  agents,  viz., 
the  hydrochloric  acid  of  the  decomposed  chlorides  and  the  carbonic  acid, 
combined  with  high  temperature  and  pressure,  quite  enough  to  account  for 
most  of  the  corrosion  which  occurs. 

The  researches  of  Stingl,  which  I  have  quoted,  show  the  power  for  evil 
which  greasy  matters  wield,  and  this  specially  I  believe  where  the  water  is 
comparatively  fresh,  though  not  there  alone.  And  where  grease  is  allowed 
to  reach  the  boilers  it  can  also  carry  along  with  it  particles  of  other  metals, 
which,  in  spite  of  the  incredulity  of  some  engineers,  have  been  found  to  do 
mischief,  and  are  capable  of  doing,  if  possible,  more  in  presence  of  salt 
water  than  with  fresh,  unless  it  be  acidulated.  It  is  not  supposed  that  they 
can  do  all  the  mischief,  or  even  any  in  places  to  which  they  cannot  reach  ; 
it  is  sufficient  that  they  are  capable  of  doing  some,  and  there  are  specimens 
extant  (among  the  specimens  collected  by  the  Admiralty  committee  on  boilers 
for  instance)  of  corrosion  and  abrasion  of  brass  tubes  and  other  parts  of 
engines,  which  show  that  this  is  a  real  and  not  a  fancied  danger. 

The  simple  explanation  of  the  fact  that  all  such  corroding  agents  have 
done  damage  principally  since  the  introduction  of  the  surface  condenser, 
is  that  the  surface  condenser,  by  separating  the  condensed  steam  from  the  sea 
water  used  to  condense  it,  and  by  returning  so  much  fresh  water  to  the 
boilers,  has  reduced  the  proportion  of  sea-water  used  in  them  below  that 
point  at  which  it  is  possible  to  form  a  protecting  scale  or  crust  by  the 
saturation  of  a  considerable  quantity  of  sea- water.  It  also,  as  I  have  said, 
provides  for  the  complete  liberation,  by  repeated  boiling,  of  the  carbonic  acid 
held  by  the  sea-water. 

That  sea-water  alone  at  the  boiling  point  corrodes  iron  is  proved  by  one  of 
Wagner's  experiments,  in  which  the  percentage  of  loss  from  a  piece  of  iron 
plate  which  was  kept  in  contact  with  boiling  sea-water  and  air  for  six  weeks, 
steadily  increased  from  0^43  per  cent,  after  one  week  to  1*24  per  cent,  after  six 
weeks.  And  proof  that  in  marine  boilers  a  small  proportion  of  sea-water  is 
capable  of  doing  mischief  while  a  large  quantity  is  not,  is  found  readily  in  the 
fact  that  engineers  have  repeatedly  arrested  corrosive'  action  by  simply  increas- 
ing the  quantity  of  sea-water  in  the  boilers,  but  without  altering  any  of  the. 
other  conditions  of  working.  It  is  always  in  boilers  that  are  "  worked  fresh  " 
(i.e.,  with  the  minimum  of  sea-water)  that  corrosion  proceeds  most  rapidly, 
and  I  know  of  one  steamer  (the  s.s.  Vespasian)  where  by  continually 
working  fresh,  a  new  set  of  boiler  tubes  was  required  in  little  more  than 
twelve  months  after  starting,  while  after  that  time,  in  the  same  boilers,  the 
use  of  a  large  proportion  of  sea-water  was  enough,  without  further  change  in 
working  to  preserve  the  boilers  from  rapid  corrosion.  As  soon  as  the 
smallest  quantity  of  scale  begins  to  form,  destructive  action  is  arrested. 


APPENDIX.  627 

This  is  true  of  all  the  various  kinds  of  destructive  action,  and  explains  how 
under  the  old  regime  none  of  these  were  known.  It  also  shows  how 
fallacious  must  be  any  conclusions  drawn  from  comparisons  of  results  with 
old  boilers  in  any  attempt  to  argue  from  them  to  results  in  modern  ones,  as 
though  both  were  obtained  under  like  conditions.  Another  proof  of  the 
existence  of  such  decompositions  as  I  have  described  is  found  in  the  fact  that 
the  water  of  boilers  in  which  corrosion  is  going  on  becomes  alkaline.  This 
shows  an  accumulation  in  solution  of  the  effect  of  the  alkaline  ingredients  of 
sea-water,  by  decomposition  and  the  neutralisation  of  the  acid  ingredients, 
and  it  is  for  this  reason  that  some  have  been  disappointed  by  testing  the 
water,  who  had  concluded  that  if  corrosion  was  due  to  the  presence  of  acid 
substances  then  the  water  must  be  acid. 

The  pitting  and  blotching  effects  produced  on  the  metal  of  the  boilers  prove 
on  examination  to  be  not  so  mysterious  as  our  first  apprehensions  render 
them.  The  same  results  follow  the  use  of  corroding  liquids  in  any  metal 
vessels  when  exposed  to  air  and  to  sight.  Even  basins  made  of  platinum — 
which  is  harder  and  closer  in  texture  than  any  other  metal — I  am  informed,  are 
found  by  chemists  to  wear  in  a  similar  way  by  having  certain  liquids  boiled 
in  them,  and  thus  the  effects  are  apparently  due  to  non-homogeneity  of  the 
metals  as  well  as  to  purity  in  some  cases.  Heat  in  most  instances  has  a  con- 
siderable share  in  directing  the  action,  which  is  usually  found  to  have  been 
more  intense  in  the  hotter  regions. 

Before  adverting  to  a  remedy  for  this  action,  I  may  say  that  in  the  boilers 
of  the  s.s.  Propontis,  analyses  of  crusts  from  which  are  given  at  page  613,  the 
various  results  of  corrosion  were  experienced.  Increase  of  density  in  the 
water  observed  when  nominally  working  with  fresh  water  alone  proves,  from 
the  analysis  of  the  deposit  then  taken  from  the  boilers,  and  from  an  estimation 
of  the  total  solids  in  the  water  at  the  close  of  that  voyage  (made  by  Mr. 
Tookey,  and  found  to  amount  to  3272-5  grains  in  the  gallon),  to  have  been 
due  to  leakage  of  sea-water  into  the  boilers  by  means  of  connections  with  a 
small  boiler  used  for  supplying  steam  to  a  cylinder  steam-jacket.  Milkiness 
and  acrid  taste  in  the  water  were  no  doubt  due  to  the  presence  of  fatty 
substances  in  solution,  as  a  large  quantity  of  grease  was  collected  on  the  filter 
through  which  all  the  feed  water  passed.  It  is  probable  that  these  two 
causes  will  be  found  to  account  in  nearly  all  cases  for  the  increase  of  density 
often  observed  in  similar  circumstances  of  working. 

It  now  remains  to  suggest  a  remedy.  Much  has  been  said  in  favour  of  the 
use  of  /inc  in  boilers,  but  zinc  will  not  do  where  any  proportion  of  sea-water 
is  used,  because  it  is  very  rapidly  decomposed  by  the  salts  in  sea- water,  and 
chloride  of  zinc  merely  adds  to  the  impurities  and  evils  of  the  case.  It  has 
been,  and  may  be,  used  successfully  in  fresh  water,  where  there  is  free  acid 
to  be  neutralised,  but  there  its  usefulness  stops  as  far  as  corrosion  is 
concerned. 

Filtering  the  feed-water  is  a  most  excellent  precaution,  and  should 
undoubtedly  be  universally  adopted  in  order  to  prevent,  as  far  as  possible,  the 
entrance  of  foreign  substances  into  the  boiler. 

To  prevent  the  corrosive  action  in  them  of  matters  in  solution,  which  no 
filter  can  arrest,  I  believe  no  better  remedy  can  be  found  than  the  forming  on 
the  interior  surfaces  an  artificial  coating  composed  of  calcium  sulphate  and 
magnesium  hydrate  in  proportions  varying  according  to  the  pressure  carried 
in  the  boiler.  This  can  be  readily  fed  in,  in  the  form  of  a  thin  whitewash, 
with  fresh  water,  and  should  be  applied  to  all  boilers  on  the  very  first 
occasions  of  getting  up  steam  in  them.  Otherwise  corrosive  actions  may 
commence,  and  unfit  the  surfaces  for  the  adherence  of  such  a  protecting 
crust.  A  protecting  crust  has  repeatedly  been  formed  in  boilers  by  using 
salt  water  ;  and  in  one  of  Mr.  Milln's  examples  he  was  able  to  keep  this  of. 
proper  thinness  by  regularly  blowing  off  about  i-9th  of  the  water  evaporated 


628  APPENDIX. 

Yet  this  is,  as  he  admits,  a  very  troublesome,  and  not  a  safe  method  of 
working,  and  yet  to  keep  such  a  scale  on,  it  must  be  carefully  carried  out 
without  intermission,  because  as  soon  as  the  boilers  are  allowed  to  "work 
fresh"  that  scale  dissolves  off.  By  making  an  artificial  scale  with  fresh 
water,  as  suggested,  its  thickness  is  quite  under  control,  and  when  once 
hardened  by  heat,  fresh  water  will  not  dissolve  it,  and  thus  steam  can  be 
generated  in  the  best  way.  Even  if  a  small  quantity  of  sea-water  should 
leak  in  it  is  not  likely  that  the  coating  would  be  injured. 

Apart  from  such  a  plan  there  seems  to  be  no  hope  of  escaping  corrosion 
and  advancing  at  the  same  time  in  engineering  practice,  until  it  is  possible  to 
have  copper  boilers.  And  yet,  even  then,  as  the  recent  experiments  of 
Carnelley  on  "The  Action  of  Water  and  of  Various  Saline  Solutions  on 
Copper"  (Chem.  Soc.  J.,  No.  clxiii.,  page  I,)  seem  to  show,  we  should  still 
have  to  combat  the  same  difficulties. 


THE  WEAR  AND  TEAR  OF  BOILERS. 

From  The  Engineer,  Sept.  I5th,  1876. 

MR.  F.  J.  Rowan,  of  Glasgow,  has  within  the  last  few  days  read  a  paper  in 
the  Mechanical  Section  of  the  British  Association  "  On  Boiler  Incrustation  and 
Corrosion."  Mr.  Rowan's  reputation  as  an  engineer  is  a  sufficient  guarantee 
that  a  paper  from  his  pen  on  such  a  subject  will  be  worthy  of  consideration, 
and  we  regret  extremely  that  he  has  requested  us  not  to  reproduce  his 
contribution  to  Section  G  in  a  complete  form.  It  is  so  compact,  and  yet  so 
involved,  that  it  would  be  impossible  to  condense  it,  and  at  the  same  time 
render  intelligible  the  statements  and  the  arguments  which  it  contains.  We 
have  no  course  left  open  to  us,  therefore,  but  to  call  attention  to  the  fact  that 
Mr.  Rowan  has  contributed  some  valuable  information  to  the  existing  stock  of 
knowledge  concerning  the  wear  and  tear  of  steam  boilers,  and  to  give  here 
some  idea  of  the  line  of  argument  which  he  has  adopted.  The  great  defect 
of  the  paper  is  want  of  lucidity.  Mr.  Rowan  publishes  facts,  opinions,  the 
results  of  experiments,  and  the  theories  and  explanations  of  a  whole  host  of 
authorities,  British  and  foreign,  without  much  attempt  at  arrangement  ;  and, 
unfortunately,  he  does  not  draw  his  deductions  with  the  clearness  which  is 
desirable,  while  he  has  omitted  certain  extremely  Important  considerations. 
It  follows  that  the  paper  must  be  read,  or  rather  studied,  with  a  great  deal  of 
care  before  we  can  arrive  at  any  definite  conclusion  as  to  Mr.  Rowan's 
meaning  ;  but,  on  the  other  hand,  when  we  have  found  out  what  this  is,  we 
admit  readily  that  his  reasoning  is  sound  as  far  as  it  goes,  and  in  some 
respects  novel,  and  no  one  will  dispute  that  the  paper  has  been  prepared  with 
great  pains,  and  that  it  displays  an  extraordinary  amount  of  special  erudition 
on  the  part  of  the  author. 

Mr.  Rowan  first  considers  the  causes  and  effects  of  incrustation  in  boilers, 
and  we  find  with  regret  that  while  he  repeats  a  great  deal  that  has  been  said 
byDr  Rogers,  of  Madison,  U.S.,  concerning  the  conducting  power  of  incrusta- 
tions of  lime,  etc.,  he  has  entirely  ignored  the  fact  that  the  conducting  power 
of  a  body  is  practically  no  measure  whatever  of  its  powers  of  transmitting 
heat.  It  has  been  shown  long  since  by  Peclet,  whose  views  have  been 
endorsed  by  Rankine,  that  the  ability  of  a  plate  of  any  substance  to  transmit 
heat  depends  far  more  on  what  has  been  termed  the  emissive  and  receptive 
powers  of  the  two  surfaces  of  the  plate  than  on  anything  else.  Thus,  for 
example,  an  iron  plate  will  conduct  about  twelve  times  as  much  heat  in  a 
given  time  as  its  surfaces  can  absorb  or  give  out.  The  principle  has  been 
utilised  by  the  employment  of  "  heat  pegs,"  or  pins  traversing  the  thickness 
of  a  boiler.  All  the  heat  which  a  surface  of  12  in.  can  absorb  is  freely 


APPENDIX.  629 

transmitted  through  a  single  square  inch  of  sectional  area  where  the  pin 
passes  through  the  plate.  That  is  to  say,  if  we  have  a  pin  i  in.  square  and 
about  6  in.  long  inserted  in  the  side  of  a  fire-box,  so  that  something  less  than 
3  in.  of  the  length  of  the  pin  are  in  the  furnace  and  the  same  length  at  the 
other  side  of  the  plate  in  the  water,  then  the  portion  of  the  pin  in  :he  fire 
cannot  be  unduly  heated,  the  sectional  area  of  the  pin  sufficing  to  convey  the 
whole  of  the  heat  absorbed  and  given  out  by  the  much  larger  surfaces  in  the 
furnace  and  the  water.  From  a  neglect  of  this  fact  Mr.  Rowan  tacitly  admits 
that  with  half  an  inch  of  scale  on  a  plate,  that  plate  can  be  made  red  hot,  or 
nearly  so  ;  and  he  also  accepts  the  statements  of  Dr.  Rogers,  to  the  effect  that 
a  scale  of  TV  in.  thick,  increases  the  consumption  of  fuel  by  15  per  cent.,  while, 
when  it  is  ^  in.  thick,  60  per  cent,  more  fuel  is  needed.  These  statements  we 
believe  to  be  extremely  incorrect.  It  has  been  shown,  indeed,  that  the  presence 
of  a  thin  scale  has  actually  increased  the  steaming  power  of  a  boiler,  simply 
because  the  surface  of  the  scale  emitted  heat  more  freely  than  a  surface  of  iron 
to  the  water  with  which  it  was  in  contact.  In  several  instances  Mr.  Rowan 
accepts  statements  which  refer  to  isolated  experiments,  or  the  deductions  of 
comparatively  unknown  experimentalists,  with  the  same  readiness  and  good 
faith.  This  is  a  serious  defect  in  so  elaborate  a  communication  ;  and  we  call 
attention  to  it  in  no  unkindly  spirit  of  criticism,  but  in  the  hope  that  when  Mr. 
Rowan  reprints  his  paper,  as  we  believe  he  proposes  to  do,  he  will  revise  it  in 
the  sense  of  explaining  to  his  readers  whether  he  does  or  does  not  hold  that 
such  reasoning,  as  that  of  Dr.  Rogers  for  example^  is  sound. 

When  we  come  to  speak  of  the  way  in  which  Mr.  Rowan  has  dealt  with 
the  chemistry  of  incrustation,  we  have  little  to  say  that  is  not  praise.  Never 
previously,  we  venture  to  affirm,  has  such  a  complete  resume  of  the  opinions 
of  chemists  been  placed  before  the  world  in  compact  form.  We  shall  make 
no  attempt  to  reproduce  this  portion  of  the  paper,  but  hasten  at  once  to  say 
that  Mr.  Rowan's  grand  panacea  for  all  the  ordinary  forms  of  incrustation  is 
the  use  of  soda  ash.  The  quantity  of  this  material  used  in  a  pair  of  boilers  at 
Barrovvfield — one  6  ft.  6  in.  by  21  ft.,  and  the  other  7  ft.  6  in.  by  27ft. — is  6  Ib. 
per  week  in  both  boilers.  The  total  quantity  of  feed  used  is  9700  gallons  per 
week.  The  soda  is  dissolved  in  water  and  pumped  into  the  boilers,  which  are 
blown  out  once  every  three  months.  The  deposit  consisted,  before  the  use  of 
the  ash,  of  carbonate  of  lime  66  per  cent.,  with  quantities  varying  from  I  to  8 
per  cent,  of  magnesia,  sulphate  of  lime,  silica,  oxide  of  iron,  etc.  The  soda 
ash  has  answered  perfectly  in  this  case,  it  would  appear.  As  regards  marine 
boilers,  Mr.  Rowan  admits  that  soda  ash  cannot  be  used,  and  that  the  only 
true  remedy  for  incrustation  at  sea  lies  in  the  use  of  fresh  water.  It  is  a 
remarkable  fact  that  he  passes  over  in  silence  the  well-known  truth  that  the 
deposit  of  lime  salts  in  a  boiler  is  due  to  the  circumstance  that  these  salts  are 
less  soluble  in  hot  water  than  they  are  in  cold  water.  If  this  were  not  the 
case,  as  we  never  have  feed-water  in  the  condition  of  a  really  saturated 
solution  of  carbonate  or  sulphate  of  lime,  incrustation  could  be  wholly 
avoided  by  blowing  off.  On  the  other  hand,  if  water  be  heated  to  212  deg., 
or  a  little  over,  before  it  is  pumped  into  a  boiler,  and  time  be  allowed  for  the 
settlement  of  the  salts  which  it  will  then  throw  down,  incrustation  may  be 
very  nearly  prevented.  It  would  be  entirely  prevented,  but  that  when  the 
water  is  raised  a  second  time  in  temperature  in  the  boiler,  a  further  quantity 
of  salts  becomes  insoluble  ;  which  is  to  say  that  that  which  just  before  was 
not  a  saturated  solution  because  its  temperature  was  212  deg.,  now  becomes 
one  because  its  temperature  is  280  cleg,  or  300  deg.  We  have  never  yet 
heard  the  truth  of  these  statements  controverted  ;  and  they  bear  so  important 
a  relation  to  the  question  discussed  by  Mr.  Rowan  that  it  is  to  be  regretted  he 
has  passed  them  over  in  silence. 

Mr.  Rowan's  conclusions  concerning  the  cause  of  corrosion  in  marine 
boilers  will  hardly  be  accepted  without  question  by  engineers.  He  arrays, 


630  APPENDIX. 

it  is  true,  an  army  of  authorities  on  his  side  ;  but  as  these  men  are  for  the 
most  part  chemists  who  have  dealt  on  a  very  small  scale  with  pieces  of  iron 
and  various  solutions,  and  have  had  no  practical  experience  with  steam  boilers, 
we  must  refuse  to  believe  that  they  have  placed  the  solution  of  a  very 
complex  problem  at  the  disposal  of  the  world.  Mr.  Rowan's  theory  is,  that 
the  corrosion  of  marine  boilers  working  with  surface  condensers  is  due  to  the 
presence  in  the  water  of  grease,  and  some  gas.  He  is  not  very  particular 
what  gas.  To  prove  this  theory  he  cites  the  experiments  of  Stingl,  Wagner, 
Fischer,  and  others.  There  is  nothing  novel  in  the  statement  that  the 
presence  of  grease  in  a  boiler  causes  corrosion  ;  but  we  believe  that  very 
many  engineers  will  join  with  us  when  we  assert  that  the  most  elaborate 
systems  of  filtering  feed-water,  and  so  excluding  grease,  have  totally  failed  to 
prevent  the  decay  of  marine  boilers.  In  fact,  the  presence  or  absence  of 
grease  has  had,  in  a  large  number  of  instances,  no  appreciable  effect  one  way 
or  another  on  the  decay  of  iron  plates,  and  at  this  moment  it  is  largely 
exaggerated.  We  do  not  dispute,  however,  that  in  several  instances  there  has 
been  some  reason  to  think  that  grease  had  an  injurious  effect,  and  it  is  highly 
desirable  for  this  and  for  other  reasons  to  keep  it  out  of  a  boiler.  As  regards 
the  theory  that  the  presence  of  air  or  some  other  gas  sets  up  and  maintains 
corrosion,  we  may  say  that,  although  the  theory  is  not  new  as  regards  air,  it 
appears  to  be  quite  novel  as  regards  other  gases.  At  least  it  is  now  put 
before  the  world  in  a  complete  and  specific  form  for  the  first  time.  It  is 
almost  as  difficult  to  prove  that  Mr.  Rowan  is  wrong  as  to  demonstrate  that 
he  is  right.  He  very  properly  points  out  that  the  water  coming  from  a  surface 
condenser  is  not  distilled  or  pure  water  in  the  chemical  sense  ;  but  that,  on 
the  contrary,  it  contains  air,  carbonic  acid  gas,  etc.  In  a  word,  pure  distilled 
water  is  never  used  at  sea  in  boilers,  and  this  being  the  case,  we  cannot  say 
from  experience  whether  pure  water  would  or  would  not  corrode  a  boiler. 
But  he  urges  that  it  is  certain  that  it  would  not  corrode  a  boiler,  because  the 
late  Professor  Crace  Calvert  found  that  distilled  water  which  did  not  contain 
air  or  gases  was  without  corrosive  action  on  iron,  a  bright  blade  immersed  in 
such  water  having  become  in  some  days  merely  here  and  there  spotted  with 
rust.  This  does  not  appear  to  us  to  be  at  all  conclusive  evidence  against  the 
corrosive  powers  of  even  pure  distilled  water.  The  spots  of  rust  were  found 
to  occur  at  places  where  "  small  impurities  in  the  iron  set  up  galvanic  action." 
Mr.  Rowan  will  not  maintain  that  boiler  plates  are  free  from  impurities,  and 
we  see  no  reason  to  doubt  that  a  boiler  supplied  with  pure  distilled  water 
would  quickly  become  spotted  with  rust,  as  did  Professor  Calvert's  polished 
iron  blade  ;  and  when  spots  of  rust  once  begin  to  form,  no  one  can  say  when 
the  process  of  deterioration  will  cease.  Besides,  it  must  not  be  forgotten  that 
Professor  Calvert  worked  with  cold  water,  not  with  hot  ;  and  one  of  the 
essential  points  in  the  arguments  of  those  who  consider  pure  water  an  enemy 
to  boiler  plates  is,  that  the  water  must  be  heated  to  a  high  temperature.  Again, 
does  not  Mr.  Rowan  beg  the  question  a  little  when  he  asserts  that  air,  or 
other  gases,  remains  in  solution  in  considerable  quantities  in  a  steam  boiler  ? 
Is  it  not  more  than  probable  that  the  air  finds  its  way,  for  the  most  part,  to 
the  steam  space,  and  thence  to  the  engine,  almost  at  once  ?  Is  there,  indeed, 
any  good  reason  to  believe  that  the  water  in  a  boiler  which  has  been  under 
steam  for  some  days  can  contain  much  free  air  ?  We  shall  not  attempt  to 
decide,  but  we  may  say  that  Mr.  Rowan  has  hardly  proved  his  case. 

After  all  Mr.  Rowan  has  written,  we  are  just  a  little  surprised  to  find  that 
he  can  suggest  no  new  remedy  for  corrosion.  The  only  cure  is,  he  admits, 
to  be  found  in  covering  all  the  surfaces  of  the  boiler  with  a  protective  coating 
of  some  salt  of  lime.  Every  sea-going  engineer  in  the  kingdom  was  aware  of 
this.  The  means  which  Mr.  Rowan  proposes  for  obtaining  the  required  pro- 
tection are  somewhat  novel,  and  consist  in  pumping  a  bucketful  of  thin  white- 
wash into  the  boiler  every  now  and  then.  Many  engineers  will  prefer  the 


APPENDIX.  631 

old  plan  of  using  a  little  sea-water  from  time  to  time  as  feed  ;  but  Mr. 
Rowan's  scheme  is  extremely  simple,  and  will,  we  have  no  doubt,  work  well. 
After  all,  however,  it  is  somewhat  unsatisfactory  to  find  that  a  man  of  Mr. 
Rowan's  great  experience  and  research,  aided,  as  he  has  been,  by  Dr. 
Wallace,  a  highly  competent  chemist,  is  unable  to  suggest  any  remedy  for 
corrosion  that  has  not  been  known  and  universally  practised  for  many  years 
with  but  indifferent  success.  If  it  is  true  that  a  scale  TV  m-  tnick  increases  the 
consumption  of  fuel  by  15  per  cent.,  as  Dr.  Rogers  would  have  us  believe, 
then  Mr.  Rowan's  remedy  for  one  evil  introduces  another  of  hardly  less 
importance.  What  the  marine  engineer  wants  to  get  rid  of  is  the  necessity 
for  obtaining  and  keeping,  with  infinite  pains  and  worry,  a  scale  in  his  boilers. 
When  Mr.  Rowan  has  failed  to  do  this,  we  much  fear  that  while  the  steam- 
engine  endures,  scale  will  have  to  be  relied  on  as  the  sole  agent  which  can 
prevent  the  rapid  destruction  of  marine  boilers. 


THE  CORROSION  AND  INCRUSTATION  OF  BOILERS. 

From  The  Engineer  of  igth  October,  1876. 

SIR, — I  have  refrained  from  replying  to  your  leading  article  of  September 
1 5th,  on  "  The  Wear  and  Tear  of  Boilers,"  until  now,  in  order  that  my  paper, 
which  you  there  review,  might  be  published,  and  so  in  the  hands  of  engineers 
generally,  and  that  I  might  have  the  opportunity  of  learning  what  others  had 
to  say  on  the  subject.  Your  review  of  my  paper  evinces  a  sufficiently  kind 
feeling  to  leave  me  without  desire  to  do  other  than  acknowledge  this  and  give 
it  full  weight  in  replying.  It  is  on  this  account  that  I  regret  to  have  to  point 
out  that  some  of  your  remarks  have  rather  the  effect  of  misrepresenting  the 
position  I  take  up  in  that  paper.  I  refer  specially  (i)  to  what  you  call  the 
"remarkable  fact  of  my  passing  over  in  silence  the  well-known  truth  that  the 
deposit  of  lime  salts  in  a  boiler  is  due  to  the  circumstance  that  these  salts  are 
less  soluble  in  hot  water  than  they  are  in  cold  water  ;"  (2)  to  your  account  of 
"  my  theory  of  the  corrosion  of  marine  boilers  working  with  surface  con- 
densers," which,  according  to  this  account,  is  that  the  action  "  is  due  to  the 
presence  in  the  water  of  grease  and  some  gas,"  while  I  am  "  not  very 
particular  what  gas  "  is  meant  ;  and  (3)  to  your  description  of  my  "  cure  "  for 
corrosion  and  the  mode  of  applying  it. 

1 i )  Instead  of  ignoring  the  fact  you  speak  of,  I  say,  on  page  614  of  my  paper, 
that  Dr.  Fischer  has  "  proved  from  a  number  of  analyses  that  various  decom- 
positions of  the  salts  contained  in   waters  take  place   under  the  influence  of 
elevated  temperature  and  pressure.  Fischer  quotes  various  authorities  to  show 
that  gypsum  gives  off  nearly  half  its  water  of  crystallisation    at  temperatures 
up  to  100  deg.  Cent.,  and  further  proportions  at  higher  temperatures,  so  that 
its  solubility  is  greatly  diminished.     Above  140  deg.  Cent,  it  becomes  totally 
insoluble  in  sea-water,  and  at  a  lower  temperature  in  fresh   water,  and  hence 
is  deposited  as  an  anhydride.     It  is  more  easily  soluble  in  water  containing 
sodium  or  magnesium  chloride  in  solution  than  in  pure  water."     I  might  have 
referred  to  earlier  demonstrations  of  these  facts,  but  preferred  to  quote   from 
Dr.  Fischer's  results  because  of  the  evident  thoroughness  of  his  work.     I  did 
not  think  it  necessary  to  enter  into  the  question  of  the  use  of  brine  chests,  be- 
cause I  believe  that  the  system  of  blowing  off,  even  with  such  a  modification, 
is  prettv  universally  condemned     at  least,  it  is  disliked  by  all  engineers  who 
have  learned  the  true  relation  of  heat  to  work. 

(2)  How  you  could  have  gathered  such  an  idea  of   my  theory  of  corrosion 
from  pages  626  and  627  of  my  paper,  which  treat  of  this  part  of  the  subject,  I 
cannot  understand.     I  had  thought  that  I  had  made  my  meaning  plain,  but 
must  have  failed  to  do  so.     Let  me  point  out  here  that  I   intended  to  indicate 


632  APPENDIX. 

very  distinctly  that  the  hydrochloric  acid  produced  by  the  decomposition  of 
the  magnesium  chloride  in  sea-water,  and  the  carbonic  acid  gas  which  sea- 
water  holds  absorbed  in  considerable  quantity,  are  "sufficient,"  as  corrosive 
agents,  "to  account  for  most  of  the  corrosion  which  occurs."  And,  besides 
these  and  the  elements  of  high  temperature  and  pressure  which  enter  into  the 
case,  I  desired  to  prove  from  the  investigations  of  Stingl  (described  on  pages 
618,  619,  and  620)  that  fatty  acids  in  solution,  obtained  from  grease,  etc.,  have 
frequently  had  a  considerable  share  in  destroying  boilers,  and  also  that  grease 
acts  both  directly,  as  in  the  cases  mentioned  by  Stingl  and  by  Jas.  Gilchrist 
(p.  623),  and  indirectly  by  inducing  galvanic  action  of  the  kind  to  which  I 
referred  on  page  623,  and  626.  Filtering  feed-water  cannot,  of  course, 
arrest  anything  which  exists  in  solution  in  that  water,  and  therefore  the 
mere  exclusion  of  solid  grease  by  such  means  cannot  prove,  as  you  would 
desire,  that  some  corrosion  is  not  due  to  grease  acting  as  I  represented  its 
action  in  my  extracts  from  Stingl's  researches  ;  but  it  is  a  great  matter  to 
exclude  all  solid  grease  and  all  metallic  and  other  foreign  particles  from  the 
boilers,  and  therefore  I  hold,  that  every  steamer  using  a  surface  condenser 
should  have  a  filter  for  the  feed-water.  Carbonic  acid  and  oxygen  were  the 
gases  to  which  I  repeatedly  referred  as  being  present  in  greater  or  less  quantity 
in  all  waters,  except  really  pure  distilled  water,  so  that  I  trust  all  doubt  as  to 
"  what  gas  "  I  meant  may  be  set  at  rest.  I  do  not  think  that  you  are  quite 
ingenuous  in  your  use  of  my  argument  as  to  pure  distilled  water.  I  am  not 
so  foolish  as  to  maintain  that  boiler  plates  are  made  free  from  impurities,  and 
therefore  have  not  stated  the  conclusion  to  which  you  seek  to  bring  my  argu- 
ment, viz.,  that  a  boiler  supplied  with  pure  distilled  water  might  not  rustirom 
that  cause.  What  I  endeavoured  to  prove  was  that  the  corrosion  with  which 
marine  engineers  are  acquainted  was  certainly  never  produced  by  pure  dis- 
tilled water,  because  such  distilled  water  has  never  been  present  to  produce 
it,  and  because  the  character  of  the  corrosion  which  has  been  produced  is  very 
different  from  that  observed  in  Calvert's  and  Wagner's  investigations  with 
distilled  water.  Under  the  circumstance  of  the  kind  of  experience  which  is 
available,  I  fear  that  it  is  idle  to  speculate  as  to  what  would  be  the  effect  of 
working  a  boiler  writh  pure  distilled  water.  As  to  the  presence  of  air — i.e., 
oxygen  and  carbonic  acid — in  the  feed-water  from  surface  condensers,  the 
fact  that  such  water  is  condensed  in  contact  with  air  is  sufficient  evidence,  I 
should  think,  for  the  majority  of  chemists  that  air  is  present  in  it.  It  is  quite 
true  that  when  this  wrater  is  boiled,  air  is  freed  or  partly  freed  from  it  ;  but  in 
what  you  say  on  this  subject  you  evidently  forget  that  fresh  quantities  of  air 
are  being  constantly  brought  back  to  the  boiler  by  the  condensed  feed-water, 
and  that  the  water  in  a  boiler  after  a  few  days'  steaming  has  probably  been 
outside  of  the  boiler,  taking  a  little  fresh  air,  several  times  during  that 
period. 

(3)  My  greatest  dissatisfaction,  I  must  say,  is  produced  by  your  concluding 
remarks  referring  to  my  cure  for  corrosion  and  the  mode  of  applying  it.  I 
do  not  think  that  \vhat  you  say  fairly  represents  my  position. 

On  page  625  I  pointed  out  the  unstable  character  of  the  scale  formed  from 
sea-water,  and  on  page  628  expressly  contrasted  with  this  the  permanent  scale 
— not  of  "  some  salt  of  lime,"  but  of  calcium  sulphate  and  magnesium  hydrate 
—to  be  produced  from  fresh  water,  which  I  proposed  ;  and  yet  you  write  as 
if  I  had  merely  suggested  a  new  method  of  doing  what  is  done  every  day — 
i.e.,  of  making  a  salt  scale.  I  am  sure  that  those  who  read  my  paper  at  all 
carefully  must  in  the  main  decide  that  you  have  not  given  much  attention  to 
that  part  of  it.  Your  description  of  my  method  of  forming  this  protecting 
coating  is  also  very  inaccurate.  I  do  not  advise  or  suggest  that  "  a  bucketful 
of  whitewash  should  be  pumped  into  the  boiler  every  now  and  then  "  ;  but  I 
say  that  the  mixture  for  producing  the  coating  can  readily  be  fed  in  in  the 
form  of  a  thin  whitewash,  and  should  be  applied  to  all  boilers  on  the  very  first 


APPENDIX.  633 

occasions  of  getting  up  steam  in  them  ;  and  that  by,  making  an  artificial  scale 
with  fresh  water,  as  suggested,  its  thickness  is  quite  under  control,  and  when 
once  hardened  by  heat,  fresh  water  will  not  dissolve  it,  and  thus  steam  can  be 
generated  in  the  best  way.  Even  if  a  small  quantity  of  sea-water  should  leak 
in,  it  is  not  likely  that  the  coating  would  be  injured.  Under  these  circum- 
stances, I  confess  to  considerable  astonishment  at  your  remark,  that  what  I 
suggest  as  a  remedy  "  has  been  known  and  universally  practised  for  many 
\cars  with  but  indifferent  success."  I  must  reply  that,  except  in  some 
instances  of  our  own,  I  do  not  believe  that  what  I  suggest  has  ever  been 
practised  at  all  as  yet,  but  that  it  does  offer  to  the  marine  engineer  a  means  of 
getting  rid  of  "  the  necessity  for  obtaining  and  keeping,  with  infinite  pains 
and  worry,  a  scale  in  his  boilers."  I  must  notice  your  parting  shot  at  me  on 
the  score  of  the  thickness  and  non-conductibility  of  the  protective  coating,  and 
I  have  two  things  to  say  :  First,  I  did  not  suggest  or  propose  to  form  a  scale 
Tle  in.  thick  ;  and,  secondly,  I  do  not  consider  a  scale  of  that  thickness  as  by 
any  means  thin.  One  special  advantage  of  my  mode  of  coating  the  boilers  I 
state  to  be  that  the  thickness  is  quite  under  control  by  it,  and  therefore  the 
scale  can  be  made  thin,  which  is  scarcely  possible  by  the  usual  plan  of  work- 
ing with  sea-water.  I  suggested  the  coating  in  full  view  of  Dr.  Rogers'  results, 
which  I  believe  to  be  in  the  main  correct,  as  they  have  not  been  disproved,  so 
far  as  I  am  aware. 

Peclet's  principles,  so  far  as  I  understand  them,  suppose,  if  they  do 
not  expressly  stipulate  for,  a  material  which  is  a  conductor  of  heat  ;  for  what 
avails  the  possession  of  a  surface  capacity  of  radiating  heat  if  the  heat 
cannot  reach  that  surface  through  the  body  of  the  material  ?  Would  any  one 
propose  to  make  heat  pegs  of  rock  or  of  anything  but  a  good  conductor, 
like  iron  ?  Thus,  though  it  may  be  true  that  a  thin  scale  has  in  some 
cases  actually  increased  the  steaming  power  of  a  boiler,  that  certainly 
would  not  justify  the  conclusion  to  which  your  reasoning  might  lead  us, 
that  the  thicker  the  scale  we  have  the  better,  in  order  that  it  may  act  as  heat 
pegs.  I  am  afraid  that  when  you  penned  your  objection  to  my  scale 
formation  on  the  score  of  thickness  and  non-conductibility,  you  had 
forgotten  your  former  remark,  that  "  it  has  been  shown  that  the  presence 
of  a  thin  scale  has  actually  increased  the  steaming  power  of  a  boiler,"  on  the 
score  of  which  remark  I  might  be  pardoned  for  citing  you  as  a  witness  in 
favour  of  my  plan.  For  I  have  only  to  show  that  I  form  a  thin  scale  to 
enable  me  to  claim  the  advantage  you  mention.  I  should  think  that  a  scale 
of  TVin.  thick  would  be  considered  by  most  boiler  proprietors  as  a  positive 
nuisance  ;  how  much  more  one  of  £  in.  or  one  of  ^  in.  ?  You  say  that 
Dr.  Rogers'  results  as  to  the  effect  of  scales  of  these  thicknesses  on  the 
temperature  and  combustion  are  "  extremely  incorrect."  Can  you  tell  me  if 
any  one  has  demonstrated  them  to  be  so,  and  if  so,  when  and  where  ?  I  have 
not  verified  them  by  experiment,  but  they  seem  to  me  to  be  not  far  off  the  mark. 

As  my  paper  was  printed  and  in  Messrs.  Spon's  hands  before  your 
article  appeared,  I  could  not  adopt  your  suggestion  as  to  declaring  my 
acceptance  in  general  of  these  results  of  Dr.  Rogers.  I  should  have  been 
glad  to  have  done  so,  had  it  been  possible,  for  those  who  had,  like  you, 
some  doubt  on  the  subject.  But  while  referring  to  this,  I  may  be  allowed  to 
say  that  I  think  I  might  without  difficulty  have  been  understood  as  quoting 
only  such  results  as  I  believed  to  be  worthy  of  acceptance,  or  at  least 
of  consideration.  I  do  not  know  that  I  have  built  upon  the  "isolated 
experiments  or  deductions  of  comparatively  unknown  experimentalists,"  but 
if  you  find  that  I  have  done  so,  I  shall  be  glad  that  you  point  out  the 

insiances-  FRED.  Jxo.  ROWAN. 

[Before  we  wrote  one  line  concerning  Mr.  Rowan's  paper,  we  read 
that  paper  twice  over  word  for  word,  and  while  commenting  on  it  we 


634  .  APPENDIX. 

constantly  referred  to  it.  We  are  quite  willing  to  admit  that  \ve  have  failed 
to  understand  Mr.  Rowan.  This  is  highly  probable,  because,  as  we  have 
already  pointed  out,  the  great  defect  of  the  paper  is  its  want  of  lucidity  ;  and 
we  confess  that  we  still  find  ourselves,  even  with  the  preceding  letter 
before  us,  uncertain  whether  we  really  understand  our  correspondent's 
meaning.  For  example,  we  have  not  the  least  idea  what  he  intends  to 
convey  by  the  words,  "  a  salt  scale."  Nothing  of  the  kind  has  ever  been 
used,  to  our  knowledge,  in  marine  boilers  working  with  high-pressure 
steam  to  protect  the  surfaces.  Salt  water  is  introduced  into  such  boilers  in 
order  that  a  thin,  hard  crust — not  of  salt,  but  of  sulphate  and  carbonate 
of  lime — may  be  formed  on  the  iron.  Under  the  conditions  it  is  simply  im- 
possible that  any  coating  of  salt  could  be  formed  or  maintained,  and  it 
appears  to  us  that  Mr.  Rowan's  plan  of  pumping  in  lime  wash  is  identical  in 
principle  with  that  of  pumping  in  sea-water.  That  is  to  stay,  the  composition 
of  the  resulting  scale  will  be  very  nearly  the  same,  whichever  expedient 
we  employ. — ED.  £.] 


From  Tlie.  Engineer  of  lyth  October,  J8/6. 

SIR, — -In  your  editorial  note  to  my  letter  of  last  week  you  allude  to  a 
point  of  considerable  importance,  and  I  therefore  ask  the  privilege  of  some 
of  your  space  for  a  few  words  upon  it.  I  have  satisfied  myself  by  the 
examination  of  a  good  number  of  analyses  of  boiler  crusts  and  deposits, 
that  all  such,  when  deposited  from  sea-water,  contain  common  salt,  or 
chloride  of  sodium,  and  other  ingredients  soluble  in  fresh  water.  I  believe, 
though  I  cannot  speak  dogmatically  upon  this  point,  that  the  proportion 
of  these  soluble  salts  in  the  crusts,  and  especially  that  of  the  chloride 
of  sodium,  increases  in  direct  ratio  to  the  pressure  of  steam  carried  in 
the  boiler  which  has  become  coated  with  such  scale.  You  will  find 
these  matters  alluded  to  on  pages  613  and  614  of  my  paper.  Thus,  a  sea-water 
scale  or  crust  contains  more  than  sulphate  and  carbonate  of  lime,  and  this  is 
a  fact  of  great  importance. 

It  is  the  presence  of  these  soluble  salts  that  renders  sea-water  scale 
so  unstable,  and  that  accounts  for  its  ready  removal  by  fresh  water,  or 
even  by  a  larger  proportion  of  fresh  water  in  the  boilers,  as  is  obtained 
by  "  working  fresh."  This  also  explains  why  such  scale  can  be  preserved 
only  by  uninterrupted  care  in  keeping  the  proper  proportion  of  sea- 
\vater  present  in  the  boilers,  for  if  the  water  becomes  fresher  the  scale 
dissolves  and  disintegrates,  and  if  the  water  is  made  more  salt  the  thickness 
of  crust  is  increased,  and  other  troubles  follow.  All  this  involves,  as 
you  have  said,  "  infinite  pains  and  worry." 

I  have  referred  to  this  on  page  625  of  my  paper,  where  I  combat  the 
opinion  of  Mr.  Milln  and  some  others  who  have  asserted  that  the  scale 
or  crust  formed  from  sea-water  is  insoluble  ;  and  it  was  with  these 
facts  before  me  that  I  denominated  such  a  scale  a  "  salt  scale,"  in  contrast  to 
the  coating  which  I  recommend. 

FRED.  JNO.  ROWAN 


The  following  is  the  letter  referred  to  on  pages  620-622  : — 

THE    CORROSION     OF     BOILERS. 
To  THE  EDITOR  OF  "ENGINEERING." 

SIR, — I  believe  that  the  remarks  on  this  subject  in  your  article  of  October 
the  c;th  on  "  Boilers  in  the  Royal  Navy,"  will  do  good  service  by  throwing 


APPENDIX.  635 

open  a  very  important  subject,  and  giving  a  proper  direction  to  the  thoughts 
of  those  who  are  interested  in  it. 

There  is  no  doubt  that  the  experience  you  describe  with  the  boilers  in  her 
Majesty's  ships  has  been  pretty  generally  known  in  the  merchant  service 
also,  where  indeed  it  has  been  that  compound  engines  with  surface  con- 
densers have  been  carried  into  general  practice  against  such  difficulties  as 
are  spoken  of.  I  do  not  believe  that  these  difficulties  are  as  yet  properly 
overcome  in  general  practice,  although  in  many  instances  this  one  of  the 
corrosion  of  the  boilers  has  been  counteracted  by  the  method  now  (as  I 
understand  you)  to  be  introduced  into  the  navy,  viz.,  that  of  using  salt  water 
in  the  boilers  to  such  an  extent  as  to  cause  the  formation  of  a  protecting 
scale  on  their  interior  surfaces. 

This,  howrever,  is  evidently  only  a  makeshift,  useful  enough  until  better 
means  are  adopted  for  protecting  the  boilers  from  decay,  but  a  plan  which 
has  many  disadvantages,  not  the  least  of  these  being  that  in  it  careless 
engineers  have  the  means  of  doing  serious  injury  to  the  boilers  as  well  as 
of  interfering  with  their  economical  and  efficient  working,  by  using  too  large 
a  proportion  of  sea-water,  and  so  allowing  the  formation  of  too  thick  a  deposit 
of  salt.  Besides  this  it  offers,  as  you  remark,  no  solution  of  the  nature  of  the 
operations  which  result  in  the  corrosion  of  the  boilers,  and  until  these 
operations  are  understood  it  will  be  impossible  to  strike  at  the  root  of  the 
evil.  Moreover,  as  we  are  in  marine  engine  practice  advancing  surely  to  the 
use  of  higher  pressures  of  steam,  and  these  as  surely  demand  boilers  having 
small  sectional  areas  (and  there  are  many  considerations  which  render  such 
boilers  of  great  importance  to  naval  service),  there  is  additional  reason  at  the 
present  time  for  the  investigation  of  this  subject,  because  in  view  of  boilers 
composed  of  small  sections,  such  as  water-tube  boilers,  the  formation  of 
saline  deposit  becomes  increasingly  objectionable. 

I  should  like  to  give  you  the  results  of  some  observations  which  I  think 
will  be  of  some  interest,  and  may  add  at  the  least  a  ray  to  the  illumination 
of  this  subject.  But  first  a  few  words  as  to  your  remarks. 

You  are  undoubtedly  right  in  ascribing  to  pressure  the  power  of  intensify- 
ing chemical  action  in  general,  and  therefore  a  fortiori  ihe  corrosive  action 
which  takes  place  in  boilers  ;  but  while  you  admit  pressure  as  an  element  in 
considering  the  action  of  distilled  water  upon  the  iron,  you  omit  to  give  it  its 
place  with  regard  to  the  action  of  the  acids  which  are  set  free  by  the  heat  of 
the  steam  from  the  fatty  matters  used  in  lubricating,  and  as  a  considerable 
quantity  of  oil  and  tallow  passes  daily  through  cylinders,  etc.,  the  quantity  of 
these  acids  formed  cannot  be  contemptible.  I  think  that  on  this  account  you 
have  not  given  sufficient  place  to  the  power  of  these  acids,  under  the  circum- 
stances in  which  they  can  act,  to  act  as  solvents  of  the  iron,  and  although  it 
is  no  doubt  true  that  they  are  "  not  capable  of  doing  all  the  mischief,"  yet  a 
great  deal  may  be  done  by  them  as  direct  corrosive  agents  intensified  in  their 
action  by  high  pressure  and  temperature,  and  also  by  their  acidifying  the 
water  of  the  boilers,  and  so  constituting  it  a  more  active  medium  for  galvanic 
action.  It  is  well  known  that  dilute  acid,  as  one  of  the  elements  of  a  battery, 
is  much  more  active  in  exciting  galvanic  action  than  water  alone  in  the  same 
position  is,  and  therefore  we  have  another  reason  in  this  for  regarding  the 
presence  of  these  fatty  acids  as  a  serious  evil,  and  also  a  reason  for  giving 
greater  weight  than  you  allow  to  the  power  of  galvanic  action  to  assist  in 
effecting  corrosion. 

"Tinning  the  condenser  tubes  has  not,"  as  you  say,  "arrested  corrosion 
of  the  boilers,"  and  I  would  add  that  neither  has  it  arrested  galvanic  action  in 
the  boilers,  for  this  is  really  caused  by  particles  of  brass  or  copper  from  the 
engine  or  condenser  (from  air  pump,  or  valves,  or  piston  rings,  or  condenser 
tubes,  etc.),  being  carried  into  the  boilers  by  grease,  which  collects  several  of 
them  into  one  lump,  and  by  this  metallic  lump  being  brought  into  contact 


636  APPENDIX. 

with  the  iron  of  the  boiler  in  presence  of  the  acid  medium.  A  very  active 
battery  exists  at  the  points  where  such  lumps  rest,  and  the  iron  under 
its  action  rapidly  passes  into  solution  and  into  the  state  of  magnetic  oxide, 
leaving  a  rough  or  honeycombed  surface. 

Pure  water  no  doubt  does  dissolve  iron,  and  the  best  practical  demonstra- 
tion of  this  action  that  I  know  was  afforded  us  at  my  late  father's  works  (the 
Atlas  Works  in  Glasgow),  where  we  found  a  range  of  horizontal  multitubular 
boilers  being  rapidly  acted  upon  by  the  Loch  Katrine  water  which  was  used 
in  them,  and  which,  as  is  well  known,  is  sufficiently  pure  to  be  used  in 
chemical  laboratories  without  distillation.  As  these  boilers  were  used  for 
working  steam  hammers  and  high  pressure  non-condensing  engines,  there 
was  no  chance  of  galvanic  action  such  as  I  have  described,  and  therefore  the 
interior  surfaces  of  the  tubes  were  wasted  evenly,  until  steps  were  taken  by 
the  introduction  of  limestone  into  the  water  of  the  boilers  to  arrest  this 
action.  The  use  of  pieces  of  limestone  in  the  boilers  had  the  desired  effect, 
so  that  it  is  not  difficult  to  prevent  the  action  of  pure  water  ;  but,  in  fact,  this 
is  an  action  which  can  exist  only  in  a  modified  degree  in  marine  practice, 
because  the  water  of  the  boilers  is  not  pure,  but  is  alwaj's  more  or  less  con- 
taminated by  fatty  and  other  matters,  even  where  an  admixture  of  salt  water 
is  not  used. 

Corrosion  of  the  boilers  was  one  of  the  principal  causes  of  the  failure  of 
many  of  the  early  examples  of  the  compound  engines  and  boilers  on  our 
(Rowan  and  Morton's)  plan,  commencing  with  the  s.s.  Thetis,  in  1858, 
whose  boilers  suffered  from  this  action  after  a  few  years'  work.  This 
naturally  led  to  much  attention  being  devoted  to  this  subject,  and  as  these 
boilers  were  of  the  sectional  or  water-tube  class,  working  at  a  steam  pressure 
of  I2olb.  per  square  inch,  and  using  nothing  but  fresh  water  supplied  by 
condensation  when  at  sea,  they  offered  opportunities  for  the  observation  of  all 
the  corrosive  forces  acting  in  circumstances  the  most  favourable  for  them. 
When  I  tell  you  that  six  of  these  marine  boilers  worked  for  from  eight 
to  ten  years  at  their  original  pressure  of  120  Ib.  per  square  inch  without 
repairs  being  necessary,  you  will  readily  understand  that  means  were  at 
length  adopted  which  practically  overcame  in  these  boilers  the  corrosive 
action  which  had  proved  so  disastrous  in  many  of  their  predecessors  and 
contemporaries. 

The  boilers  of  two  steamers  belonging  to  the  London  and  Mediterranean 
Steam  Navigation  Company  were  among  those  on  our  system  which  were 
destroyed  by  corrosion  after  only  a  short  life,  and  I  have  before  me  a  copy  of 
the  report  to  the  chairman  of  the  Board  given  by  Mr.  Thomas  Spencer,  an 
analytical  chemist  who  was  consulted  on  the  subject.  Mr.  Spencer  attributed 
the  corrosion  entirely  to  the  action  of  the  fresh  or  distilled  water,  basing  his 
opinion  on  the  fact  that  the  oxide  of  iron  formed  in  contact  with  the  steam 
and  water  was  in  great  part  magnetic  (and  not  ordinary  rust),  while  it  had 
been  observed  that  cast  iron  when  acted  upon  by  distilled  water  produced  the 
same  oxide.  He  proposed  the  use  of  a  small  quantity  of  silicate  of  soda  or 
potash  in  the  boilers  as  an  antidote,  but  I  am  not  aware  if  this  was  tried.  I 
have  given  you  my  reasons  for  believing  that  galvanic  action  forms  part  of 
the  forces  at  work  in  corrosion,  and  I  think  that  such  action  sufficiently 
accounts  for  the  formation  of  the  magnetic  oxide  observed  by  Mr.  Spencer, 
but  nevertheless  I  believe  that  his  hint  as  to  the  use  of  silicate  of  soda  or 
potash  in  the  boiler  (or  feed  water,  which  amounts  to  the  same  thing)  is  a 
valuable  one. 

In  the  case  of  those  boilers  which  worked  successfully  for  so  long  a  time, 
to  which  I  have  referred,  the  means  used  for  the  preservation  of  th'e  boilers 
were  simple.  First,  all  the  water  discharged  by  the  air  pump  was  passed 
through  a  filter — a  chamber  in  the  feed  tank  filled  with  sand  or  charcoal — 
and  this  arrested  all  grease  and  all  metallic  particles  on  their  way  from  the 


APPENDIX.  673 

engines  to  the  boilers.  Then  pieces  of  zinc  were  inserted  at  various  parts  of 
the  boilers,  and  as  acid  has  a  greater  affinity  for  zinc  than  for  iron  the  fatty 
acids  expended  their  energy  on  the  formation  of  salts  of  zinc,  and  the  iron 
escaped  while  the  zinc  plates  corroded  away.  I  believe  these  precautions 
were  accompanied  by  the  occasional  use  of  lime,  a  little  of  which  was  put 
into  the  feed  water,  but  this  was  not  of  great  importance  in  the  case  of 
these  boilers,  as  they  had  the  opportunity  of  replenishing  their  supply 
of  fresh  water  pretty  frequently  in  port,  their  voyage  not  being  of  long 
duration. 

'  Lately  I  had  an  opportunity,  during  a  voyage  of  the  s.s.  Propontis,  which 
is  fitted  with  our  boilers  working  at  150  Ib.  per  square  inch,  of  observing  the 
working  ol  these  plans,  which,  in  her  case,  and  also  in  that  of  the 
s.s.  Constantin  (formerly  the  Haco,  a  steamer  trading  from  French  ports, 
and  now  in  her  filth  year)  are  continuing  to  act  satisfactorily.  In  the 
Propontis  pieces  of  limestone  along  with  the  zinc  were  put  into  all  the 
chambers  of  the  boilers  containing  water,  but  on  the  suggestion  of  Mr.  A.  C. 
Kirk  we  have  discontinued  using  the  limestone  in  those  chambers  immediately 
over  the  fires,  as  it  is  very  probable  that  the  high  temperature  at  these  points 
sets  the  carbonic  acid  of  the  limestone  free,  and  thus  more  harm  may  be  done 
than  good  by  the  presence  of  the  lime.  The  filter  in  her  case  is  filled  with 
the  ordinary  bone  charcoal  used  in  sugar  refining,  and  the  evidences  of  grease 
and  particles  ol  metal  (brass  and  copper)  arrested  by  it  have  been  abundant. 
I  have  examined  frequently  the  black  grease  taken  from  the  exterior  of  the 
filter,  and  found  it  full  of  small  metallic  particles. 

The  increase  of  the  density  of  the  water  to  which  you  call  attention  was 
observed  during  the  voyage,  and  somewhat  baffled  us,  as  it  could  not  be 
accounted  for.  Your  supposition  that  it  is  caused  by  the  amount  of  iron  in 
solution  is  not,  1  am  afraid,  the  solution  of  the  phenomenon,  as*  I  tested  for 
iron  by  the  colour  test  on  more  than  one  occasion,  the  water  from  the 
Propontis's  boilers,  which  showed  this  increased  density,  but  found  no  iron 
present  in  sensible  quantity.  Lime  and  zinc  I  did  find  present,  but  I  am  not 
sure  whether  I  can  now  secure  the  samples  of  the  water  in  order  to  have 
quantities  estimated.  I  cannot  at  this  moment  lay  my  hands  on  the  note  of 
the  densities  recorded  by  the  salinometer,  but  shall  communicate  them  if  they 
can  be  found.  They  were,  howrever,  sometimes  considerably  above  the  point 
at  which  water  in  boilers  using  salt  water  is  supposed  to  be  too  salt,  and 
must  be  blown  off  ;  but  as  you  describe,  the  taste  was  more  nauseous  than 
salt,  but  it  was  not  astringent  enough  to  indicate  a  large  quantity  of  iron  in 
solution.  I  do  not  think  that  we  have  sufficient  information  to  lead  to  a 
definite  judgment  as  to  the  cause  of  the  increased  density,  though  in  con- 
tinuous working  the  gross  quantity  of  water  being  .constant,  the  accumulation 
of  all  foreign  matters  which  are  not  volatile  must  affect  the  density  of  the 
water  more  or  less  ;  and  perhaps  some  part  of  the  effect  may  be  due  to  the 
total  expulsion  (by  repeated  boiling)  of  all  air  or  other  gases  held  in  suspension 
in  the  water. 

As  I  did  not  observe  your  paper  until  Monday  last,  I  have  somewhat 
hurriedly  thrown  these  thoughts  together  in  order  to  help  if  I  can  in  the 
elucidation  of  what  is  a  very  important  subject  in  connection  with  engineering 
wherever  high  pressures  and  surface  condensation  are  in  use  or  wanted.  In 
conclusion,  let  me  bring  some  of  the  more  important  points  together.  As  to 
the  causes  of  corrosion  these  are,  I  believe  : — 

1.  The  action  of  fatty  acids  from  the  lubricants,  intensified,  by  pressure  and 
temperature,  whether  acting  directly  as  solvents  of  the  iron,  or  indirectly  by 

2.  Galvanic  action  caused  by  particles  of   brass   and   copper   carried  by 
grease  to  the  boiler,  where,  in  contact  with  the  iron  and  with  the  acidulated 
water,  they  form  an  active  battery. 

3.  The  action  of  distilled  water  in  a  modified  degree. 


638  APPENDIX. 

For  the  prevention  of  corrosion,  or  counteracting  these  forces,  \ve  are  led 
to  the  following  remedies  : 

1.  The  use  of  zinc  in  the  boilers  to  neutralise  the  acids. 

2.  The* use  of  a  filter  for  all  the  water  passing  into  the  boiler  to  arrest  all 
grease  and  metallic  particles  ;  and, 

3.  The  use  of  lime  or  some  alkaline  mineral  in  the  boiler,  or  in  the  feed 
tank,  to  neutralise  the  action  of  the  distilled  water,  and  also  to  give  a  base  for 
any  acid  not  neutralised  by  the  /inc. 

I  quite  agree  with  you,  from  the  observation  of  the  phenomena  of  the 
increase  of  density,  that  additional  tests  to  that  of  the  hydrometer  or  salino- 
meter  are  required  on  board  ship,  and  as  the  chemical  tests  for  lime,  common 
salt  (or  chlorine),  and  iron  are  very  simple,  it  would  be  very  advantageous  if 
engineers  knew  how  to  use  them,  and  did  so  when  occasion  offered. 

Yours  faithfully, 

FRED  Jxo.  ROWAN. 
Glasgow,  2  ist  October,  1874. 


INDEX. 


PAGE 

Air  Pressure  in  Combustion  ...          ...          ...          ...          ...  91 

Air  and  Feed  Heaters  Compared     ...          97 

Absorption  of  Gases  by  Liquids        ...          ...          ...          ...  338 

Absorption,  Co-efficients  of  ...          339 

Almy  Boiler     ...          ...          ...          ...          ...          ...          ...  49=5 

Albans  Boiler 375 

Allen  Boiler      ...          ...          ...          ...          369,524 

Andrews'  Boiler          ...  450 

Anderson's  Boiler        ...          485 

American  Boiler  Trials           ...          ...  517 

America,  Water-tube  Boilers  in  Navy         ...          ...          ...  592 

Blechynden's  Experiments 162,  243 

Bryant's  Experiments             177 

Boiling,  Circulation  by            ...          ...          ...  270 

Bernoulli's  Theorem ...          ...          ...  252 

Boiler  Design,  Historical  Sketch  of 355 

Belleville  Boilers                                           ...            377,  553>  559 

Benson's  Boiler           ...          ...          ...          381 

Babcock  &  Wilcox  Boilers    ...          389,  558,  60 1 

Blechynden  Boiler      ...          ...          ...          ...          ...          ...  452 

Boilers  with  Gas  Producers ...         ...  505 

Boilers  in  Recent  Cruisers     ...          ...          ...          ...          ...  560 

British  Navy,  Boilers  in  the 561 

Carnot's  Law IXI 

Carpenter,  Professor,  Tests  of  Effects  of  Temperature     ...  310 

Clerk  Maxwell,  Prof.,  on  "  Boiling "            ...         ...         ...  220 

,,         .,         „         „        Convection  Currents    ...  221 


xxvi.  INDEX. 

PAGE 

Conduction  of  Heat    ...         ...         ...  114 

Conductivity,  Coefficient  of  ...          ...          ...          115 

Conductivity  of  Metals           118 

Cowles  Boiler 546 

Copper  and  Alloys,  Strength  of        ...         ...         313 

Chasseloup-Loubat  Experiments,  and  Calculations...         234,  256 

Circulation  of  Water  ...         ...         ...         ...         ...         ...  218 

Circulation  of  Water,  Appliances  for  Measuring 247 

Circulation  of  Water,  Artificial         - 259 

Circulation  of  Water,  Forced            259 

Climax  Boiler 493 

Craddock's  Boiler       427,54° 

Church's  Boilers         424 

Clark's  Boiler 423 

Cast-Iron  Boilers        364 

Cornut's  Remarks  on  Tests  at  High  Temperature 318 

Corrosion  of  Boilers  ...          ...          ...          ...             321,  607,  631 

Clarke  &  Motley's  Boiler       422 

Coil  Boilers      479 

Cellular  Boilers           481 

Combustion,  Theoretical  Temperature  of  ...         ...         ...  57 

Combustion,  Volume  of  Gases  from             ...         ...         ...  63 

Combustion,  Effects  of  Pre-heating  the  Air  for     ...          ...  67 

Combustion  Chambers,  External      ...          ...          ...          ...  72 

Combustion,  Forced  ...         ...         ...         ...  72 

Combustion,  Rapidity  and  Intensity  of        ...          76 

Combustion,  Admiralty  System  of 76 

Combustion,  Howden's  System  of    ...          82 

Combustion,  Closed  Ashpit  System  of         84 

Combustion,  Suction  System  of         ...          ...          ...          ...  86 

Combustion  under  Increased  Pressure        ...         ...         ...  103 

Cruisers,  Boilers  in     ...  560 

"  Clyde  "  Boiler          574 

Ductility  and  Tenacity,  Influence  of  Temperature  on       ...  271 

«  Dakota  "  s.s.  Boiler... 385 

Delayed  Ebullition 265 

Draught,  Forced  or  Accelerated       ...          ...          ...  71,  73 

Deformation  of  Boilers,  Measurements  of             ...         ...  13 

Draught,  Companon  of  Power  in  Different  Systems       ,..  73 


INDEX.  xxvii 

PAGE 

Down-comers  ...         ...         ...         ...         ...         ...         ...  230 

Dust  Fuel         ...         ...         ...         ...         ...         ...         ...  101 

Diirr  Boiler      ...          ...          ...          ...          ...         ...          ...  412 

Du  Temple  Boiler      449 

Dance  &  Field's  Boiler          475 

De  Laval's  Boiler       498,601 

Donkin's  Experiments            534 

Durston's  Marine  Boiler  Results       557 

Durston's  "  Machinery  of  Warships  "          ...          ...          ...  562 

D'Allest  Boiler            ...  566 

Expansion  of  Heat,  Force  exerted  by         26 

Evaporation     ...         ...         ...         ...         ...         ...         ...  147 

Electrical   and    Magnetic  Equivalent  of   Transmission   of 

Heat          ...  198 

Elasticity,  Modulus  of            ...  281 

"  Emulseur  "  Tubes 236 

Electrical  Activity  of  Oxides...          ...          334 

Elder's  (John)  Boiler ...  476 

Eve's  Boiler     ...         ...         ...         ...         ...         ...         ...  423 

Exeter  Boiler 370 

Evaporation  Results 512,  553,  577 

Elephant  Boilers         ...         ...  550 

Fluid  Pressure,  Pascal's  Law  of       ...         ...         ...         ...  10 

Fatigue  of  Metals        ...  19 

Feed-Heaters  and  Air-Heaters  Compared ...  97 

Feed-Water,  Heating 265 

Fletcher's  4<  Thimble  "  Boiler           490 

Film  Evaporating  System      ...          ...          ...          ...          ...  261 

Fire  Gases        ...         ...         ...         ...         ...         ...         ...  141 

Flash  Boilers ...          ...          ...          ...  360 

Flaws  and  Joints,  Effects  of  in  Heating       156 

Fracture  at  High  and  Low  Temperatures 275 

Field's  Boiler 435 

Fryer's  Boiler ...          ...          ...  440 

Fleming  &  Ferguson's  Boiler            ...         ...  451 

Fletcher's  Trials         533 

Furnace  Gases  Calculations 537 

French  Navy,  Boilers  in        565,585 

Graham's  Experiments  ,         ,..         ••• 

Y 


xxviii  INDEX. 

PAGE 

Grease,  Effects  of,  on  Heat  Transmission  ...         ...         ...     159 

Galvanic  Action  ...         ...         ...         ...         ...         ...     329 

Green's  Boiler...  ..         ...         ...         ...         ...         ...     433 

Gurney  Boiler ...         ...         457,472 

Gibbs'  Boiler ...         ...     490 

Gas  Producers,  Boilers  with ...          . .  ...         ...         ...     505 

Hudson's  Formula      ...         ...         ...         ...         ...         ...     205 

Heat,  Transmission  of  ...         ...         ...    109,150,198,604 

Harrison's  Boiler         367 

Hagemann's  Experiments     ...     125 

Hot  Gases,  Movement  of       ...          ...         ...          ...         ...     192 

Hancock's  Boilers       ...         ...         ...         ...         ...         374,484 

Horizontal  Tube  Boilers        ...         ...         ...     370 

Hardingham's  Boiler ..         ...         ...         ...     399 

Heine  Boiler    ...         ...         ...         ...         ...         ...         ...     408 

Horizontal  Tube  Boiler,  Modifications  of  the        ...         ...     419 

Horizontal  Chamber  Boilers...          ...         ...         ...         ...     420 

Howard's  Boilers        ...         ...         439,519 

Haythorn  Boilers        ...         ...  470,  575,  601 

Herreshoff's  Boilers    ...         ...         ...         ...         480 

Hazleton  Boilers         ...         ...     490 

Hudson's  Tables         ...         ..  ...         ..."        ...         ...     597 

Incrustation     ...         ...          ...         156,  321,  607,  631 

Isherwood's  Trials      ...          ...         ...         ...         513 

James's  Boiler ...          ...         ...         ...         ...     427 

Johnson's  Boiler          ...         ...         ...         ...         ...         ...     429 

Jordan's  Boiler  ...         ...         ...     437 

Jardine's  Boiler  ...          ...         ...         ...     461 

Kemp's  Feed  Heater...          ...         ...       92 

Kollmann's  Experiment?        ...         ...         ...         ...         ...     294 

Kelly  Boiler ...         ...     412 

Kennedy's  Experiments  with  Thorny  croft  Boiler  ...          ...     552 

Kennedy's  Experiments  with  Niclausse  Boiler      570 

Knut  Sty ffe's  (Prof.)  Investigations      ...         ...         ...     275,317 

Lang's  Experiments  ...         ...         ...         ...     134 

Loss  of  Heat  from  Opening  Furnace  Doors  ...          ...       59 

11  Layers "  of  Gases    ...         ...         ...         ...         ...         ...     195 

Lagraf el  D'Allest  Boilers       ...         ...         ...         ...         409,555 

Lamb  &  Summers  Boilers     ...         ...         ...         ...         ...     485 


INDEX.  xxix 

PAGE 

Levassor  &  Panhard's  Boiler            ...          ...  489 

Maxwell  (Clerk)  on  Convection  Currents    ...         ...         ...  221 

Matthey's  Experiments          ...         222 

Movement  of  Water 225 

Marten's,  Professor,  Report  on  German  Experiments       ...  300 

Mill  Scale,  Effects  of  in  Corrosion    ...          ...          ...          ...  334 

Magnesic  Chloride,  Action  of            ...          ...          ...          ...  350 

Miller's  Boiler...          ...          365 

"  Montana  "  s.s.  Boiler           ...   '       385 

Maceroni  &  Squire's  Boiler  ...          ...          ...          ...          ...  426 

Maxim's  Boiler            ...          453 

Mumford's  Boiler       ...         ...         ...         453,575 

Mosher's  Boiler  ...         456, 573 

Matheson's  Boiler       ...          476 

McCurdy's  Boiler ...  485 

Minerva  Boiler            ...          ...          ...          ...          ...          ...  492 

Miscellaneous  Boiler  Designs            492 

Mulhouse  Trials           ...  512 

Marine  Boilers  ...          ...          540,542 

Marine  Boiler  Trials 548 

Marine  Boilers,  Corrosion  in 622 

Mail  Steamers,  Boilers  in       ...         ...         ...         ...         ...  564 

Nichol's  Experiments '       130 

Northern  Railway  of  France  Experiments 143 

Niclausse  Boiler          187,  403,  567,  585 

Normand  Boiler           451 

Oscillatory  Strains       ...          ...          19,21 

Oriolle  Boiler 411 

Perry's  Formula  for  Transmission  in  Fluids           199 

Piezometer,  Theory  of  the 251 

Priming            ...  264 

Parker's  Experiments            ...         ...         ...  294 

Pressure  and  Temperature,  Influence  of     ...         343 

Points,  Influence  of 344 

Protective  Boiler  Coatings ;         ...  353 

Perkins,  Jacob,  System  of      362 

Perkins  and  Williamson  Boiler         384 

Phleger  Boiler             407 

Poole  Boiler ...  409 


xxx  INDEX. 

PAGE 

Petersons'  Boiler         ...          ...          .,.          ...  461 

Phillips' Boiler             468 

Panhard  &  Levassor's  Boiler            ...         ...         ...         ...  489 

Pierce  Boiler  ...         ...         ...         ...         ...  489 

Porcupine  Boilers       ...          ...          ...          ...          ...          ...  490 

Payne's  Evaporative  Result  ...          ...          ...          ...          ...  512 

Philadelphia  Exhibition,  1876,  Boilers  at  the         526 

Philadelphia  Electrical  Exhibition,  1884,  Boilers  at  the  ...  571 

Reichsanstalt  Experiments    ...         ...         ...         ...         ...  173 

Row's  Experiments    ...         ...         ...         ...         ...         ...  191 

Rankine's  Formula     ...         ...         ...         ...         ...         ...  212 

Reynolds,  Prof.  O.,  on  Heat  Transmission ...  121 

Revolving  Boilers        ...         357, 489 

Ramsden's  Boiler        388 

Root's  Boiler ...         ...          ...         ...  393 

Rainey's  Boiler            ...         ...         ...         ...  417 

Rowan  &  Horton's  Boilers    ...          ...          ...            431,  485,  540 

Rowan's  Boiler           ...         ...         ...  441 

Reed's  Boiler  ...         ...         ...  453 

Roberts'  Boiler            ...         ...         ...         ...         495 

Strength  in  Relation  to  Form  and  Dimensions      10 

Strains  due  to  Heating           ...          ...  22 

Stress  and  Corrosion  ...         ...         ...         ...  333 

Ser's  Results    ...         ...         ...         ...         ...         ...         ...  131 

Smith's  (Prof.  R.  H.)  Formula          200 

Steam,  Rapid  Formation  of  ...         ...          ...         227 

Sectional  Steam  Boilers         ...         ...  357 

Smith's  (Andrew),  Boiler        ...          ...          ...  375 

Suckling's  Boiler         ...         ...         ...         ...         ...         ...  397 

Steinmiiller  Boiler       ...      •  ...         ...         ...         ...         ...  401 

Seaton  Boiler  ...         ...         ...         ...         ...  409 

Summers  &  Ogle's  Boiler      ...         ...         ...         ...         ...  424 

Seabury  Boiler            457 

Symon-House  Boiler ...         ...         ...         ...  457 

Stirling's  Boiler           ...          ...          ...          ...  459 

Stevenson's  Boiler      ...         ...  466 

Simpson  &  Bodman's  Boiler...          ...          ...          ...         501,580 

Sinclair  Boiler 533 

"  Swatara "  s.s.  Boilers           ...         ...         547 


INDEX.  xxxi 

PAGE 

Single-Ended  Cylindrical  Boilers     ...          ...     554 

Scotch    &    Locomotive    Shell    Boilers    Compared    with 

Tubulous  Boilers  ...          ...          ...          ...          ...     586 

Temperature  of  Exit  Gases  ...          ...         ...       69 

Thornycroft  Boilers 89,444,481,498,552 

Thornycroft's  Experiments   ... 237 

Transmission  of  Heat ...          ...    109,  150,  198,  604 

Tenacity  and  Ductility,  Infiuence  of  Temperature  on      271,  299 
Temperature  and  Pressure    ...         ...         ...         ...         ...     343 

Teschemacher's  Boiler  ...         ...         ...         ...         ...     360 

Towne  Boiler  ...          ...          ...          416 

Trevethick's  Boilers    ...          ...          ...          ...          ...          ...     425 

Twibill's  Boiler  437 

Thorn's  Boiler 468 

Teissier's  Boilers         ...         ...         ...         ...         ...         ...     483 

Tests  of  Boilers  and  Results  ...         511 

"Thetis"  s.s 517 

Vertical  Water-Tube  Boilers  ...         ...     422 

"  Victory  "  Steamer  Boilers 545 

Witz's  Experiments    ...          ...          ...          ...          ...         ...     215 

Water,  Circulation  of ...          ...          ...          ...          ...          ...     218 

WTertheim's  Experiments       ...          ...          ...          ...          ...     274 

Woolf's  Boiler 363 

Wilcox's  Boiler  381 

Williamson  &  Perkins  Boiler        ....          ...          ...          ...     384 

Watt's  Boiler 396 

Williamson's  Boiler    ...          ...          ...          ...          ...          ...     434 

Wiegand  Boiler  ...          ...          ...          ...          ...          ...     439 

White's  Boiler  ...          ...          ...          ...          ...          ...     444 

Weir  Boiler     ...         ...         ...         ...         ...         ...         456,601 

Ward's  Boiler ...         ...         ...  458,  477,  546 

Water-Tube  and  Elephant  Boiler  Tests      ...         550 

Water-Tube  Boilers,  Durability  of 589 

Wear  and  Tear  of  Boilers     ...         ...         628 

Yarrow's  Experiments  on  Down-comers ...     232 

Yarrow's  Boiler  ...         ...         448,466 

Zander's  Boiler  485 

"  Zenith  City  "  Steam  Boilers        ^*=*-^***^      545 


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BEGTRTJP,  JULIUS,  M.  E.     The  Slide  Valve  and  its 

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BERNTHSEN,  A.     A  Text-Book  of  Organic  Chemistry. 

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BERTIN,  L..  E.     Marine   Boilers :    Their   Construction 

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CAMPIN,   FRANCIS.      On  the  Construction    of  Iron 

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CHARPENTIER,  PAUL.     Timber  ;  a  Comprehensive 

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CHAUVENET,  Prof.  W.     New  Methpd  of  Correcting 

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CLARK,   D.   KINNEAR,   C.E.      A  Manual  of  Rules, 

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CLARK,  JACOB  M.      A  new  System  of  Laying  Out 

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OLAUSEN-THUE,  W.  The  ABC  Universal  Com- 
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Financiers,  Merchants,  Ship-owners,  Brokers,  Agent,  etc.  Fourth 
Edition.  8vo,  cloth s $5.00 

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CLAUSEN-THUE,  W.    The  Al  Universal  Commercial 

Electric  Telegraphic  Code.  Over  1240  pp.,  and  nearly  90,000  varia- 
tions. 8vo,  cloth $7.50 

CLEEMANN,   THOS.   M.      The  Railroad    Engineer's 

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Construction.  4th  ed. ,  revised  and  enlarged.  Illus.  12mo,  cloth  $1.50 

CLEVENGER,   S.   R.    A  Treatise  on  the  Method  of 

Government  Surveying  as  prescribed  by  the  U.  S.  Congress  and 
Commissioner  of  the  General  Land  Office,  with  complete  Mathe- 
matical, Astronomical  and  Practical  Instructions  for  the  use  of  the 
United  States  Surveyors  in  the  field.  16mo,  morocco $2.50 

COFFIN,  Prof.  J.  H.  C,  Navigation  and  Nautical  As- 
tronomy. Prepared  for  the  use  of  the  U.  S.  Naval  Academy.  New 
edition.  Revised  by  Commander  Charles  Belknap.  52  woodcut  illus- 
trations. 12mo,  cloth net,  $3.50 

COLE,  R.  S.,  M.  A.   A  Treatise  on  Photographic  Optics. 

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Photography.  12 mo,  cloth.  103illustrationsand  folding  plates .  $2. 50 

COLLINS,  JAS.  E.    The  Private  Book  of  Useful  Alloys 

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COOPER,    W.   R.,   M.  A.      Primary  Batteries  ;    their 

Construction  and  Use.  With  numerous  figures  and  diagrams.  8vo, 
cloth,  illustrated net,  $4.00 

CORNWALL,  Prof.  H.  B.  Manual  of  Blow-pipe  An- 
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Determinative  Mineralogy.  8vo,  cloth,  with  many  illustrations.  .$2.50 

COWELL,    W.  B.      Pure   Air,   Ozone   and  Water;    a 

Practical  Treatise  of  their  Utilization  and  Value  in  Oil,  Grease,  Soap, 
Paint,  Glue  and  other  Industries.  With  tables  and  figures.  12mo, 
cloth,  illustrated net.  $2.00 

CRAIG,  B.  F.    Weights  and  Measures.    An  account  of 

the  Decimal  System,  with  Tables  of  Conversion  for  Commercial  and 
Scientific  Uses.  Square  32mo,  limp  cloth 50 

CROCKER,  R  B.  Electric  Lighting.  A  Practical  Ex- 
position of  the  Art.  For  use  of  Engineers,  Students,  and  others  inter- 
ested in  the  Installation  or  Operation  of  Electrical  Plants.  Vol.  I. 
The  Generating  Plant,  fourth  Edition,  revised.  8vo,  cloth,  illus- 
trated   $3.00 

Vol.  II.  Distributing  Systems  and  Lamps.  /Second  edition.  8vo,  cl., 
illustrated. .  $3.00 


SCIENTIFIC  PUBLICATIONS.  11 


CROCKER,  F.  B.,  and  S.  S.  WHEELER.  The  Practical 

Management  of  Dynamos  and  Motors.  Fifth  Edition,  (Eleventh 
thousand)  revised  and  enlarged.  With  a  special  chapter  by  H.  A. 
Foster.  12mo,  cloth,  illustrated 551.00 

DAVIES,  E.  H.      Machinery  for  Metalliferous  Mines. 

A  Practical  Treatise  for  Mining  Engineers,  Metallurgists  and  Manu- 
facturers. With  upwards  of  300  illustrations.  8vo,  cloth $5.00 

-  D.  C.     A  Treatise  on  Metalliferous  Minerals  and 

Mining.  Sixth  edition,  thoroughly  revised  and  much  enlarged  by 
his  son.  8vo,  cloth net,  $5.00 

MINING  MACHINERY...  ..In  Press. 


DAY,  CHARLES.     The  Indicator  and  its  Diagrams. 

With  Chapters  on  Engine  and  Boiler  Testing  ;  Including  a  Table  of 
Piston  Constants  compiled  by  W.  H.  Fowler.  12mo,  cloth.  125 
illustrations $2.00 

DENNY,  G.  A.     Deep-level  Mines  of  the  Rand,  and 

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view.  With  folding  plates,  diagrams  and  tables.  4to,  cloth,  illus- 
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DERR,  W.   L.    Block  Signal  Operation.    A  Practical 

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DIETERICH,    KARL.      Analysis  of  Resins,  Balsams 

and  Gum  Resins  ;  their  Chemistry  and  Pharmacognosis.  For  the  use 
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raphy. Translated  from  the  German,  by  Chas.  Salter.  8vo,  cloth. 
net,  $3.00 

DIXON,  D.  B.      The  Machinist's  and  Steam  Engineer's 

Practical  Calculator.  A  Compilation  of  Useful  Rules  and  Problems 
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DODD,    GEO.      Dictionary  of   Manufactures,   Mining, 

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DORR,  B.  F.    The  Surveyor's  Guide  and  Pocket  Table 

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With  a  second  appendix  up  to  date.  16mo,  morocco  flaps $2.00 

DRAPER,  C.  H.    An  Elementary  Text  Book  of  Light, 

Heat  and  Sound,  with  Numerous  Examples.  Fourth  edition.  12mo, 
cloth.  Illustrated $1.00 


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DRAPER,  C.  H.    Heat  and  the  Principles  of  Thermo- 

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cloth $1.50 

DUBOIS,  A.  J.    The  New  Method  of  Graphic  Statics. 

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Maximum    Stresses    under    Concentrated    Loads. 

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EISSLER,  M.    The  Metallurgy  of  Gold;   a  Practical 

Treatise  on  the  Metallurgical  Treatment  of  Gold-Bearing  Ores,  in- 
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Assaying,  Melting  and  Refining  of  Gold.  Fifth  Edition,  revised 
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-  The  Hydro-Metallurgy  of  Copper.  Being  an  ac- 
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Copper  Ores.  With  numerous  diagrams  and  figures.  8vo,  cloth, 
illustrated net,  $4.50 


-The  Metallurgy  of  Silver;  a  Practical  Treatise  on 

the  Amalgamation,  Boasting  and  Lixivatiou  of  Silver  Ores,  including 
the  Assaying,  Melting  and  Befining  of  Silver  Bullion.  124  illustra- 
tions. Second  Edition,  enlarged.  8vo,  cloth $4.00 

-  The  Metallurgy  of  Argentiferous  Lead ;  a  Practical 

Treatise  on  the  Smelting  of  Silver-Lead  Ores  and  the  Befining  of 
Lead  Bullion.  Including  Beports  on  Various  Smelting  Establish- 
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Europe  and  America.  With  183  illustrations.  8vo,  cloth $5.00 

-  Cyanide  Process  for  the  Extraction  of  Gold  and  its 

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Africa.  Second  edition  enlarged.  Illustrations  and  folding  plates. 
8vo,  cloth. , $3.00 

-  A  Hand-book  on  Modern  Explosives,  being  a  Prac- 
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Mtro- Glycerine  and  other  Explosive  Compounds,  including  the  man- 
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application.         Second  Edition,    enlarged  with   150    illustrations. 
12mo,  cloth $5.00 


SCIENTIFIC  PUBLICATIONS.  13 


ELIOT,  C.  W.,  and  STORER,  F.  H.     A  Compendious 

Manual  of  Qualitative  Chemical  Analysis.  Revised  with  the  co-oper- 
ation of  the  authors,  by  Prof.  William  R.  Nichols.  Illustrated. 
Twentieth  Edition,  newly  revised  by  Prof.  W.  B.  Lindsay. 
12mo,  cloth net  $1.25 

ELLIOT,  Maj.  GEO.  H.  European  Light-House  Sys- 
tems. Being  a  Report  of  a  Tour  of  Inspection  made  in  1873.  51 
engravings  and  21  woodcuts.  8vo,  cloth  $5.00 

ELLISON,    LEWIS   M.     Practical  Application  of  the 

Indicator.  With  reference  to  the  Adjustment  of  Valve  Gear  on  all 
styles  of  Engines.  Second  Edition,  revised.  8vo,  cloth,  100  illus- 
trations  $2.00 

ERFURT,  JULIUS.  Dyeing  of  Paper  Pulp ;  a  practi- 
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others.  With  illustrations  and  157  patterns  of  paper  dyed  in  the  pulp, 
with  formulas  for  each.  Translated  into  English  and  edited,  with  ad- 
ditions, by  Julius  Hiibner,  F.  C.  S.  8vo,  cloth,  illustrated,  .net.  $7.50 

EVERETT,  J.  D.     Elementary  Text-Book  of  Physics. 

Illustrated.     Seventh  Edition.     12mo,  cloth $1.50 

EWING,  Prof.  A.  J.     The  Magnetic  Induction  in  Iron 

and  other  metals.  Third  edition,  revised.  159  illustrations.  8vo, 
cloth . $4  00 

FAIRIE,  JAMES,  F.  G.  S.    Notes  on  Lead  Ores  ;  their 

Distribution  and  Properties.     12 mo,  cloth $1.00 

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With  tables  and  formulae.  12mo,  cloth $1 .50 

FANNING,  J.  T.      A  Practical  Treatise  on  Hydraulic 

and  Water-Supply  Engineering.  Relating  to  the  Hydrology,  Hydro- 
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America.  180  illustrations.  8vo,  cloth.  Fifteenth  Edition,  re- 
vised, enlarged,  and  new  tables  and  illustrations  added.  650 
pages '. $5.00 

FISH,  J.  C.  L.  Lettering  of  Working  Drawings.  Thir- 
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FISKE,  Lieut.  BRADLEY  A.,  U.S.N.     Electricity  in 

Theory  and  Practice ;  or,  The  Elements  of  Electrical  Engineering. 
Eighth  Edition.  8vo,  cloth $2.50 

FISHER,   H.   K.    C.   and  DARBY,   W.   C.      Students' 

„—  Guide  to  Submarine  Cable  Testing.     8vo,  cloth $2.50 

FISHER,  W.  C.     The  Potentiometer  and  its  Adjuncts. 

8vo,  cloth $2.25 


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FLEISCHMANN,  W.  The  Book  of  the  Dairy.  A  Man- 
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German,  by  C.  M.  Aikman  and  R.  Patrick  Wright.  8vo,  cloth... $4. 00 

FLEMING,  Prof.  J.  A.  The  Alternate  Current  Trans- 
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Currents;  611  pages.  New  edition.  Illustrated.  8vo,  cloth . . . $5. 00 
Vol.  2,  The  Utilization  of  Induced  Currents.  Illustrated.  8vo, 
cloth $5.00 

—  Centenary    of  the  Electrical  Current,  1799-1899. 

8vo,  paper,  illustrated 5o 

Electric  Lamps  and  Electric  Lighting.      Being  a 

course  of  four  lectures  delivered  at  the  Royal  institution,  April-May, 
1894.     8vo,  cloth,  fully  illustrated ; $3.00 

-  Electrical  Laboratory  Notes  and  Forms,  Elemen- 
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A  Handbook  for  the  Electrical  Laboratory  and 

Testing  Boom.     Vol.  I.     8vo,  clotb. $5.00 


FOLEY,    NELSON    and    THOS.    PRAY,    Jr.        The 

Mechanical  Engineers'  Reference  Book  for  Machine  and  Boiler  Con- 
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— Boiler  Construction.  With  fifty-one  plates  and  numerous  illustra- 
tions, specially  drawn  for  this  work.  Folio,  half  morocco $25.00 

FORNEY,  MATTHIAS  N.  Catechism  of  the  Locomo- 
tive. Second  Edition,  revised  and  enlarged  Forty- sixth  thousand. 
8vo,  cloth $3.50 

FOSTER,  Gen.  J.   G.,  U.S.A.      Submarine  Blasting  in 

Boston  Harbor,  Massachusetts.  Removal  of  Tower  and  Corwin 
Rocks.  Illustrated  with  7  plates.  4to,  cloth  $3.50 

FOSTER,  H.  A.      Electrical  Engineers'  Pocket  Book. 

With  the  Collaboration  of  Eminent  Specialists.  A  handbook  of  use- 
ful data  for  Electricians  and  Electrical  Engineers.  With  innumerable 
tables,  diagrams  and  figures.  Second  edition,  revised.  Pocket  size, 
full  leather,  1000  pages $5.00 

FOSTER,   JAMES.      Treatise  on  the  Evaporation  of 

Saccharine,  Chemical  ard  other  Liquids  by  the  Multiple  System  in 
Vacuum  and  Open  Air.  Second  Edition.  Diagrams  and  large 
plates.  8vo,  cloth  $7.50 

FOX,  WM.,  and  C.  W.  THOMAS,  M.  E.    A  Practical 

Course  in  Mechanical  Drawing.  Second  edition,  revised.  12mo, 
cloth  with  plates $1.25 


SCIENTIFIC  PUBLICATIONS.  15 


FRANCIS,  Jas.  B.,  C.E.  Lowell  Hydraulic  Experi- 
ments. Being  a  selection  from  experiments  on  Hydraulic  Motors, 
on  the  Flow  of  Water  over  Weirs,  in  open  Canals  of  uniform  rec- 
tangular section,  and  through  submerged  Orifices  and  diverging 
Tubes.  Made  at  Lowell,  Mass.  Fourth  edition,  revised  and 
enlarged,  with  many  new  experiments,  and  illustrated  with  23 
copper- plate  engravings.  4to,  cloth $15.00 

FROST,  GEO.  H.     Engineer's  Field  Book.      By  C.   S. 

Cross.  To  which  are  added  seven  chapters  on  Railroad  Location  and 
Construction.  Fourth  edition.  12mo,  cloth $1.00 

FULLER,  GEORGE  W.     Report  on  the  Investigations 

into  the  Purification  of  the  Ohio  River  Water  at  Louisville,  Ken- 
tucky, made  to  the  President  and  Directors  of  the  Louisville  Water 
Company.  Published  under  agreement  Avith  the  Directors.  3  full 
page  plates.  4to,  cloth ntt,  $10.00 

GARCKE,  EMILE,   and  J.    M.    FELLS.     Factory  Ac- 

counts  ;  their  principles  and  practice.  A  handbook  for  accountants  and 
manufacturers,  with  appendices  on  the  nomenclature  of  machine  de- 
tails, the  rating  of  factories,  fire  and  boiler  insurance,  the  factory  and 
workshop  acts,  eta. ,  including  also  a  large  number  of  specimen  rul- 
ings. Entirely  new  and  revised  edition.  8vo,  cloth,  illus../^  Press. 

GEIPEL,  WM.  and  KILGOUR,  M.  H.    A  Pocketbook 

of  Electrical  Engineering  Formulae.     Illustrated.     18mo,  mor.  .$3.00 

GERBER,   NICHOLAS.     Chemical  and  Physical  An- 

alysis  of  Milk,  Condensed  Milk  and  Infant's  Milk-Food.  8vo, 
cloth $1.25 

GERHARD,  WM.  P.      Sanitary  Engineering.      12mo, 

cloth  $1.25 

GESCHWIND,  LUCIEN.     Manufacture  of  Alum  and 

Sulphates,  and  other  Salts  of  Alumnia  and  Iron  ;  their  uses  and  ap- 
plications as  mordants  in  dyeing  and  calico  printing,  and  their  other 
applications  in  the  Arts,  Manufactures,  Sanitary  Engineering,  Agri- 
culture and  Horticulture.  Translated  from  the  French  by  Charles  Sal- 
ter.  With  tables,  figures  and  diagrams.  8vo,  cloth,  illus..  .net.  $5.00 

GIBBS,  WILLIAM  E.  Lighting  by  Acetylene,  Gen- 
erators, Burners  and  Electric  Furnaces.  With  66  illustrations.  Sec- 
ond edition  revised.  12mo,  cloth $1.50 

GILLMORE,  Gen.  Q.  A.     Treatise  on  Limes,   Hyraulic 

Cements,  and  Mortars.  Papers  on  Practical  Engineering,  United 
States  Engineer  Department,  No.  9,  containing  Reports  of  numerous 
Experiments  conducted  in  New  York  City  during  the  years  1858  to 
1861,  inclusive.  With  numerous  illustrations.  8vo,  cloth $4.00 

GILLMORE,  Gen.  Q.  A.  Practical  Treatise  on  the  Con- 
struction of  Roads,  Streets,  and  Pavements.  Tenth  Edition.  With 
70  illustrations.  12mo,  cloth $2.00 


16  D.  VAN  NOSTRAND  COMPANY'S 


Report  on  Strength  of  the  Building  Stones  in  the 

United  States,  etc.    8vo,  illustrated,  cloth $1.00 

GOLDING,    HENRY    A.      The    Theta-Phi    Diagram. 

Practically  applied  to  Steam,  Gas,  Oil  and  Air  Engines.  12nio,  cloth. 
Illustrated net,  $1 .25 

GOODEVE,  T.  M.    A  Text-Book  on  the  Steam-Engine. 

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143  illustrations.  12mo,  cloth. . .  '  . . ' $2.00 

GORE,  G.,  F.  R.  S.  The  Art  of  Electrolytic  Separa- 
tion of  Metals,  etc.  (Theoretical  and  Practical.)  Illustrated.  8vo, 
cloth $3.50 

GOULD,  E.  SHERMAN.     The  Arithmetic  of  the  Steam 

Engine.     8vo,  cloth SI. 00 

GRIFFITHS,  A.   B.,   Ph.D.     A  Treatise  on  Manures, 

or  the  Philosophy  of  Manuring.  A  Practical  Hand-Book  for  the 
Agriculturist,  Manufacturer,  and  Student.  12mo,  cloth $3.00 

GROSS,  EMANUEL.  Hops,  in  their  Botanical,  Agri- 
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lated from  the  German  by  Charles  Salter.  With  tables,  diagrams  and 
illustrations.  8vo,  cloth,  illustrated net.  $4.50 

GROVER,  FREDERICK.  Practical  Treatise  on  Mod- 
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GRUNER,  ANTON.      Power-loom  Weaving  and  Yarn 

Numbering,  according  to  various  systems,  with  conversion  tables.  ALI 
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industry.  Illustrated  with  colored  diagrams.  8vo,  cloth. .  .net.  $3.00 

GURDEN,    RICHARD    LLOYD.      Traverse    Tables: 

computed  to  4  places  Decimals  for  every  °  of  angle  up  to  100  of  Dis- 
tance. For  the  use  of  Surveyors  and  Engineers.  New  Edition. 
Folio,  half  morocco $7.50 

GUY,  ARTHUR  F.     Electric  Light  and  Power,  giving 

the  Result  of  Practical  Experience  in  Central-Station  Work.  8vo, 
cloth.  Illustrated $2.50 

HAEDER,   HERMAN,   C.  E.       A  Handbook    on    the 

Steam  Engine.  With  especial  reference  to  small  and  medium  sized 
engines.  English  edition,  re-edited  by  the  author  from  the  second 
German  edition,  and  translated  with  considerable  additions  and  alter- 
ations by  H.  H.  P.  Powles.  12mo,  cloth.  Nearly  1100  illus.  .  .$3.00 

HALL,  WM.  S.   Prof.      Elements  of  the  Differential 

and  Integral  Calculus.  Fourth  edition,  revised.  8vo,  cloth  Illus- 
trated   net,  $2.25 

Descriptive  Geometry,  with  numerous  Problems 

and  Practical  applications.     Two  vols.  (Plates  and  Text) .  ..In  Press. 


SCIENTIFIC  PUBLICATIONS.  17 


HALSEY,  F.   A.    Slide  Valve  Gears,  an  Explanation 

of  the  action  and  Construction  of  Plain  and  Cut-off  Slide  Valves. 
Illustrated.  12mo,  cloth.  Seventh  Edition $1. 50 

-  The  Use  of  the  Slide  Rule.    With  illustrations  and 

folding  plates.  Second  edition.  16mo,  boards.  (Van  Nostrand's 
Science  Series,  No.  114.) '. $0.50 

The  Locomotive  Link  Motion,  with  Diagrams  and 

Tables.     8vo.  cloth,  illustrated $1.00 

Worm  and  Spiral  Gearing.      16 mo,  cloth,  (Van  Nos- 

trand's  Science  Series,  No.  116).     Illustrated $0.50 

HAMILTON,  W.  G.    Useful  Information  for  Railway 

Men.  Tenth  Edition,  revised  and  enlarged.  562  pages,  pocket 
form.  Morocco,  gilt $2.00 

HANCOCK,  HERBERT.    Text-Book  of  Mechanics  and 

Hydrostatics,  with  over  500  diagrams.      8vo,  cloth ..$1.75 

HARRISON,     W.     B.      The    Mechanics'    Tool    Book. 

With  Practical  Rules  and  Suggestions  for  use  of  Machinists,  Iron- 
Workers,  and  others.  Illustrated  with  44  engravings.  12mo, 
cloth, $1.50 

HART,    JOHN    W.        External    Plumbing    Work;    a 

Treatise  on  Lead  Work  for  Hoofs.  With  numerous  figures  and  dia- 
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HAUFF,  W.  A..   American  Multiplier ;  Multiplications 

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HAUSNER,  A.    Manufacture  of  Preserved  Foods  and 

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HAWKINS,  C.  C.,  and  WALLIS,  F.      The  Dynamo ; 

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HAY,     ALFRED.      Principles    of  Alternate  -  Current 

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HEAVISIDE,    OLIVER.        Electromagnetic    Theory. 

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HERRMANN,     Gustav.      The    Graphical    Statics    of 

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HERMANN,   FELIX.     Painting  on  Glass  and  Porce- 

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SCIENTIFIC  PUBLICATIONS.  19 


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HOFF,  WM.  B.,  Com.  U.  S.  Navy.     The  Avoidance  of 

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HOSPITALLER,  E.     Polyphased  Alternating  Currents. 

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HOWORTH,  J.     Art  of  Repairing  and  Riveting  Glass, 

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HUMBER,  WILLIAM,  C.  E.    A  Handy  Book  for  the 

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HURST,    GEO.  H.,  F.  C.  S.      Color;    a    Hand-book    of 

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HURST,  GEO.  H.,  F.  C.  S.    Lubricating  Oils,  Fats  and 

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HUTCHINSON,  W.  B.  Member  of  the  New  York  Bar. 
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HUTTON,  W.  S.  Steam  Boiler  Construction.  A  Prac- 
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The   Works'    Manager's    Hand-Book  of   Modern 


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INNES,  CHARLES  H.    Problems  in  Machine  Design, 

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Centrifugal  Pumps,  Turbines,  and  Water  Motors. 

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ISHERWOOD,  B.  F.  Engineering  Precedents  for  Steam 

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JAMESON,   CHARLES    D.      Portland  Cement.      Its 

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JAMIESON,  ANDREW,  C.E.     A  Text-Book  on  Steam 

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Elementary  Manual  on  Steam  and  the  Steam  En- 
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JANNETTAZ,  EDWARD.  A  Guide  to  the  Determina- 
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Brooklyn  Polytechnic  Institute.  12nio,  cloth $1.50 


SCIENTIFIC  PUBLICATIONS.  21 


JEHL,  FRANCIS.  Member  A.  I.  E.  E.  The  manu- 
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numerous  diagrams,  tables  and  folding  plates.  8vo,  cloth,  illus- 
trated  $4.00 

JENNISON,  FRANCIS  H.    The  Manufacture  of  Lake 

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different  processes  of  production.  8vo,  cloth,  illustrated  .  .net,  S3. 00 

JOHNSTON,  Prof.  J.  F.  W.,  and  CAMERON,  Sir  Chas. 

Elements  of  Agricultural  Chemistry  and  Geology.  Seventeenth  Edi- 
tion. 12mo,  cloth $2.60 

JONES,  HARRY  C.      Outlines    of   Electrochemistry. 

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JONES,  M.  W.      The  Testing  and  Valuation  of  Raw 

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JOYNSON,  F.  H.      The  Metals  used  in  Construction. 

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KANSAS  CITY  BRIDGE,  THE     With  an  Account  of 

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KAPP,  GISBERT,  C.E.  Electric  Transmission  of  Ener- 
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KEMP,  JAMES  FURMAN,  A.  B.,  E.  M.  A  Hand- 
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KEMPE,   H.   R.      The    Electrical    Engineer's    Pocket 

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22  D.  VAN  NOSTRAND  COMPANY'S 


KENNELLY,  A.  E.  Theoretical  Elements  of  Electro- 
Dynamic  Machinery.  8vo,  cloth $1.50 

KZLGOTJR,  M.  H.,  SWAN,  H.,  and  BIGGS,  C.  H.  W. 

Electrical  Distribution  ;  Its  Theory  and  Practice.  174  Illustrations. 
12mo,  cloth $4.00 

KING,  W.  H.    Lessons  and  Practical  Notes  on  Steam. 

The  Steam-Engine,  Propellers,  etc.,  for  Young  Marine  Engineers, 
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KINGDON,  J.  A.  Applied  Magnetism.  An  introduc- 
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KIRKALDY,   Wm.   G.    Illustrations  of  David  Kirk- 

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KIRKWOOD,   JAS.   P.     Report    on   the    Filtration  of 

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KNIGHT,  AUSTIN  M.,  (Lieutenant- Commander  IT.  S.  M) 
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HOLLER,    THEODOR.        The    Utilization    of   Waste 

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LAMBERT,  THOMAS  Bone  Products  and   Manures: 

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LAMPRECHT,  ROBERT.     Recovery  Work  after  Pit 

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LARRABEE,  C.  S.  Cipher  and  Secret  Letter  and  Tele- 
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SCIENTIFIC  PUBLICATIONS.  23 


LASSAR-COHN,  Dr.  An  Introduction  to  Modern  Sci- 
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ty Extension  Students  and  general  readers.  Translated  from  the  au- 
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Pattison  Muir,  M.  A.  12mo,  cloth,"  illustrated $2.00 

LEASK,  A.  RITCHIE.      Breakdowns  at  Sea  and  How 

to  Repair  Them.     With  eigthy-nine  illustrations.     Second  Edition. 
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—  Triple  and   Quadruple    Expansion    Engines    and 

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Refrigerating  Machinery :  Its  Principles  and  Man- 
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LECKY,  S.  T.  S.    "  Wrinkles  "  in  Practical  Navigation. 

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LEFEVRE,    LEON.      Architectural   Pottery:  Bricks, 

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and  W.  Moore  Binns.  4to,  cloth,  illustrated net  $7.50 

LEHNER,  SIGMUND.     Ink  Manufacture :    including 

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and  Herbert  Robson,  B.  Sc.  8vo,  cloth,  illustrated,  162  pages. 
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LEVY,   C.   L.     Electric  Light  Primer.     A  Simple  and 

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safety.  For  the  use  of  persons  whose  duty  it  is  to  look  after  the 
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LIVACHE,  AC'H..—(fngenieifr  Civil  De*  Mines.)  The  Man- 
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The  Manufacture,  Employment  and  Testing  of  Various  Varnishes 
Translated  from  the  French,  by  John  Geddes  Mclntosh.  Greatly 
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24  D.  VAN  NOSTRAND  COMPANY'S 


LOBBEN,  PEDER,  M.  E.    Machinists'  and  Draftsmen's 

Hand-Book,  containing  Tables,  Rules  and  Formulas,  with  numerous 
examples,  explaining  the  principles  of  mathematics  and  mechanics,  as 
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all  interested  in  Mechanical  work.  Illustrated  with  many  cuts  and 
diagrams.  8vo,  cloth $2.50 

LOCKE,  ALFRED  G.  and  CHARLES  G.     A  Practical 

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tive  Plates  drawn  to  Scale  Measurements,  and  other  Illustrations- 
Royal  8vo,  cloth $10. 00 

LOCKERT,    LOUIS.      Petroleum    Motor-Cars.    12mo, 

cloth $1.50 

LOCKWOOD,  THOS.  D.     Electricity,  Magnetism,  and 

Electro-Telegraphy.  A  Practical  Guide  for  Students,  Operators,  and 
Inspectors.  8vo,  cloth.  Third  Edition $2.50 

-  Electrical  Measurement  and  the  Galvanometer ;  Its 

Construction  and  Uses.  Second  Edition,  32  illustrations.  12mo, 
cloth $1.50 

LODGE,  OLIVER  J.  Elementary  Mechanics,  includ- 
ing Hydrostatics  and  Pneumatics.  Revised  Edition.  12mo, 
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LODGE,  OLIVER  J.  Signalling  Across  Space,  With- 
out Wires  ;  being  a  description  of  the  work  of  Hertz  and  his  successors. 
With  numerous  diagrams  and  half  tone  cuts,  and  additional  remarks 
concerning  the  application  to  Telegraphy  and  later  developments. 
Third  edition.  8vo,  cloth,  illustrated net,  $2.00 

LORD,  R.  T.  Decorative  and  Fancy  Fabrics.  A  val- 
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signers of  Carpets,  Damask,  Dress  and  all  Textile  Fabrics.  8vo, 
cloth,  illustrated net,  $3. 50 

LORING,  A.  E.    A  Hand-Book  of  the  Electro-Magnetic 

Telegraph.    Cloth,  boards.     New  and  enlarged  edition 50 

LUCE,   Com.   S.   B.      Text-Book  of  Seamanship.    The 

Equipping  and  Handling  of  Vessels  under  Sail  or  Steam.  For  the 
use  of  the  U.  S.  Na\al  Academy.  Revised  and  enlarged  edition, 
by  Lt.  Win.  S.  Benson.  8vo,  cloth $10.00 

LUNGE,    GEORGE.    Ph.  D.     Coal-Tar  and  Ammonia; 

being  the  third  and  enlarged  edition  of  "A  Treatise  on  the  Distilla- 
tion of  Coal-tar  and  Ammomacal  Liquor,"  with  numerous  tables,  fig- 
ures and  diagrams.  Thick  8vo,  cloth,  illustrated net  $15.00 

A  Theoretical  and  Practical  Treatise  on  the  Man- 
ufacture of  Sulphuric  Acid  and  Alkali  with  the  Collateral  Branches. 
Vol.  I.  Sulphuric  Acid.  Second  Edition,  Revised  and  enlarged. 

342  illustrations.     8vo,  cloth $15.00 

Vol.  II.  Second  Edition,  revised  and  enlarged.  8vo,  cloth.  .$16.80 
Vol.  III.  8vo,  cloth.  New  Edition,  1896 $15.00 


SCIENTIFIC  PUBLICATIONS.  25 


LUNGE,  GEO.,  and  HURTER,  F.    The  Alkali  Maker's 

Pocket  Book.  Tables  and  Analytical  Methods  for  Manufacturers  of 
Sulphuric  Acid,  Nitric  Acid,  Soda,  Potash  and  Ammonia.  Second 
Edition.  12mo,  cloth $3.00 

LUQUER,  LEA  McILVAINE,   Ph.   D.      Minerals  in 

Rock  Sections.  The  Practical  Method  of  Identifying  Minerals  in 
Rock  Sections  with  the  Microscope.  Especially  arranged  for 
Students  in  Technical  and  Sientific  Schools.  8vo,  cloth.  Illus- 
trated  net,  $1.50 

MACCORD,  Prof.  C.  W.    A  Practical  Treatise  on  the 

Slide- Valve  by  Eccentrics,  examining  by  methods  the  action  of  the 
Eccentric  upon  the  Slide- Valve,  and  explaining  the  practical  processes 
of  laying  out  the  movements,  adapting  the  Valve  for  its  various 
duties  in  the  Steam-Engine.  Second  Edition.  Illustrated.  4to, 
cloth $2.50 

MACKROW,  CLEMENT.     The  Naval  Architect's  and 

Ship-Builder's  Pocket-Book  of  Formulae,  Rules  and  Tables ;  and 
Engineers'  and  Surveyors'  Handy-Book  of  Reference.  Seventh  edi- 
tion. 16mo,  limp  leather,  illustrated.. .  .  $5.00 

MAGUIRE,  Capt.    EDWARD,  U.  S.  A.      The  Attack 

and  Defence  of  Coast  Fortifications.  "With  Maps  and  Numerous 
Illustrations.  8vo,  cloth $2.50 

MAGTJIRE,  WM.   R.        Domestic  Sanitary  Drainage 

and  Plumbing  Lectures  on  Practical  Sanitation.  332  illustrations. 
8vo  $i.OO 

MARKS,  EDWARD   C.  R.      Mechanical    Engineering 

Materials  :  Their  Properties  and  Treatment  in  Construction.  12mo, 
cloth.  Illustrated 60 

Notes  on  the  Construction,  of  Cranes  and  Lifting 

Machinery.  With  numerous  diagrams  and  figures.  New  and  en- 
larged edition.  12tno,  cloth net,  $1.50 

MARKS,   G.    C.       Hydraulic   Power    Engineering :     a 

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by  Hydraulic  Machinery.  With  over  two  hundred  diagrams  and 
tables.  8vo,  cloth,  illustrated $3.50 

MAVER,  WM.     American  Telegraphy :     Systems,  Ap- 
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MAYER,   Prof.   A.    M.       Lecture    Notes    on  Physics. 
8vo,  cloth $2.00 

McCULLOCH,    Prof.    R.   S.      Elementary  Treatise  on 

the  Mechanical  Theory  of  Heat,  and  its  application  to  Air  and  Steam 
Engines.  8vo,  cloth $3. 50 


26  D.  VAN  NOSTRAND  COMPANY'S 


McNEILL,    BEDFORD.      McNeilTs  Code.      Arranged 

to  meet  the  requirements  of  Mining,  Metallurgical  and  Civil  Engi- 
neers, Directors  of  Mining,  Smelting  and  other  Companies,  Bankers, 
Stock  and  Share  Brokers,  Solicitors,  Accountants,  Financiers,  and 
General  Merchants.  Safety  and  Secrecy.  8vo,  cloth  $6.00 

McPHERSON,  J.  A.  (A.  M  Inst.  C.  E.)  Waterworks 
Distribution  ;  a  practical  guide  to  the  laying  out  of  systems  of  distrib- 
uting mains  for  the  supply  of  water  to  cities  and  towns.  With  tables, 
folding  plates  and  numerous  full-page  diagrams.  8vo,  cloth,  ill.  $2.50 

MERRITT,    WM.    HAMILTON.      Field    Testing    for 

Gold  and  Silver.  A  Practical  Manual  for  Prospectors  and  Miners. 
With  numerous  half-tone  cuts,  figures  and  tables.  16mo,  limp 
leather,  Illustrated $1.50 

METAL.  TURNING.     By  a  Foreman  Pattern  Maker. 

Illustrated  with  81  engravings.     12mo,  cloth $1.50 

MICHELL,  STEPHEN.  Mine  Drainage ;  being  a  com- 
plete Practical  Treatise  on  Direct- Acting  Underground  Steam  Pump- 
ing Machinery.  Containing  many  folding  plates,  diagrams  and  tables. 
Second  edition,  re-written  and  enlarged.  Thick,  8vo,  cloth,  illus. 
$10.00 

MINIFIE,  WM.  Mechanical  Drawing.    A  Textbook  of 

Geometrical  Drawing  for  the  use  of  Mechanics  and  Schools,  in  which 
the  Definitions  and  Rules  of  Geometry  are  familiarly  explained  ;  the 
Practical  Problems  are  arranged  from  the  most  simple  to  the  more 
complex,  and  in  their  description  technicalities  are  avoided  as  much  as 
possible.  With  illustrations  for  Drawing  Plans,  Sections,  and  Eleva- 
tions of  Railways  and  Machinery ;  an  Introduction  to  Isometrical  Draw- 
ing, and  an  Essay  on  Linear  Perspective  and  Shadows.  Illustrated  with 
over  200  diagrams  engraved  on  steel.  Ninth  thousand.  With  an 
appendix  on  the  Theory  and  Application  of  Colors.  8vo,  cloth.  .$4.00 

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Ninth  edition.  12ino,  cloth $2.00 

MODERN  METEOROLOGY.   A  Series  of  Six  Lectures, 

delivered  under  the  auspices  of  the  Meteorological  Society  in  1870. 
Illustrated.  12mo,  cloth $1.50 

MOORE,  E.  C.  S.  New  Tables  for  the  Complete  Solu- 
tion of  Ganguillet  and  Kutter's  Formula  for  the  flow  of  liquids  in 
open  channels,  pipes,  sewers  and  conduits.  In  two  parts.  Part  I, 
arranged  for  1,080  inclinations  from  1  over  1,  to  1  over  21,120  for 
fifteen  different  values  of  (n).  Part  II,  for  use  with  all  other  values 
of  (ri).  With  large  folding  diagram.  8vo,  cloth,  illustrated,  .net,  $5.00 

MOREING,  C.  A.,  and  NEAL,  THOMAS.  New  Gen- 
eral and  Mining  Telegraph  Code.  676  pages  alphabetically  arranged. 
For  the  use  of  mining  companies,  mining  engineers,  stockbrokers, 
financial  agents,  and  trust  and  finance  companies.  8vo,  cloth. .  .$8.40 


SCIENTIFIC  PUBLICATIONS.  27 


MOSES,  ALFRED  J.,  and  PARSONS,  C.  L.    Elements 

of  Mineralogy,  Crystallography  and  Blowpipe  Analysis  from  a  prac- 
tical standpoint.  Second  Thousand.  8vo,  cloth,  336  illns..ne£,  $2.00 

MOSES,   ALFRED    J.      The  Characters  of   Crystals. 

An  Introduction  to  Physical  Crystallography,  containing  321  Illustra- 
tions and  Diagrams.  8vo,  211  pp .-, net,  $2.00 

MULLIN,  JOSEPH  P.,  M.E.      Modern  Moulding  and 

Pattern-Making.  A  Practical  Treatise  upon  Pattern-Shop  and  Foun- 
dry Work  :  embracing  the  Moulding  of  Pulleys,  Spur  Gears,  Worm 
Gears,  Balance-Wheels,  Stationary  Engine  and  Locomotive  Cylinders, 
Globe  Valves,  Tool  Work,  Mining  Machinery,  Screw  Propellers,  Pat- 
tern-Shop Machinery,  and  the  latest  improvements  in  English  and 
American  Cupolas ;  together  with  a  large  collection  of  original  and 
carefully  selected  Eules  and  Tables  for  every-day  use  in  the  Drawing 
Office,  Pattern-Shop  and  Foundry.  12mo,  cloth,  illustrated $2.50 

MUNRO,   JOHN,  C.E.,  and  JAMIESON,  ANDREW, 

C.  E.  A  Pocketbook  of  Electrical  Rules  and  Tables  for  the 
use  of  Electricians  and  Engineers.  Fifteenth  edition,  revised 
and  enlarged.  With  numerous  diagrams.  Pocket  size.  Leather.  $2. 50 

MURPHY,  J.  G.,  M.E.     Practical  Mining.     A  Field 

Manual  for  Mining  Engineers.  With  Hints  for  Investors  in  Mining 
Properties.  16mo,  morocco  tucks $1.00 

NAQUET,  A.  Legal  Chemistry.  A  Guide  to  the  Detec- 
tion of  Poisons,  Falsification  of  Writings,  Adulteration  of  Alimentary 
and  Pharmaceutical  Substances,  Analysis  of  Ashes,  and  examination  of 
Hair,  Coins,  Arms,  and  Stains,  as  applied  to  Chemical  Jurisprudence, 
for  the  use  of  Chemists,  Physicians,  Lawyers,  Pharmacists  and  Experts. 
Translated,  with  additions,  including  a  list  of  books  and  memoirs  on 
Toxicology,  etc.,  from  the  French,  by  J.  P.  Battershall,  Ph.D.,  with  a 
preface  by  C.  F.  Chandler,  Ph.D.,  M.D.,  LL.D.  12mo,  cloth.  .$2.00 

NASMITH,  JOSEPH,    The  Student's  Cotton  Spinning. 

Third  edition,  revised  and  enlarged.  8vo,  cloth,  622  pages,  250 
illustrations $3.00 

NEUBURGER,  HENRY  and  HENRI  NOAL.HAT. 

Technology  of  Petroleum.  The  Oil  Fields  of  the  World  ;  their  His- 
tory, Geography  and  Geology.  Annual  Production,  Prospection  and 
Development.  Oil-well  Drilling,  Transportation  of  Petroleum  by 
land  and  sea.  Storage  of  Petroleum.  With  153  illustrations  and  25 
plates.  Translated  from  the  French  by  John  Geddes  Mclntosh.  8vo, 
cloth,  illustrated net,  $10.00 

NEWA.L.L,  JOHN  W.     Plain  Practical  Directions  for 

Drawing,  Sizing  and  Cutting  Bevel-Gears,  showing  how  the  Teeth 
may  be  cut  in  a  Plain  Milling  Machine  or  Gear  Cutter  so  as  to  give 
them  a  correct  shape  from  end  to  end  ;  and  showing  how  to  get  out 
all  particulars  for  the  Workshop  without  making  any  Drawings. 
Including  a  Full  Set  of  Tables  of  Reference.  Folding  Plates.  8vo, 
cloth $1.50 


28  D.  VAN  NOSTBAND  COMPANY'S 


NEWLANDS,  JAMES.    The  Carpenters'  and  Joiners' 

Assistant :  being  a  Comprehensive  Treatise  on  the  Selection,  Prepara- 
tion and  Strength  of  Materials,  and  the  Mechanical  Principles  of 
Framing,  with  their  application  in  Carpentry,  Joinery,  and  Hand- 
Bailing  ;  also,  a  Complete  Treatise  on  Sines  ;  and  an  illustrated  Glos- 
sary of  Terms  used  in  Architecture  and  Building.  Illustrated.  Folio, 
half  morocco $15.00 

NIPHER,   FRANCIS  E.,  A.M.      Theory  of  Magnetic 

Measurements,  with  an  appendix  on  the  Method  of  Least  Squares. 
12mo,  cloth $1.00 

NUGENT,  E.   Treatise  on  Optics;   or,  Light  and  Sight 

theoretically  and  practically  treated,  with  the  application  to  Fine  Art 
and  Industrial  Pursuits.  With  103  illustrations.  12mo,  cloth. .  .$1.50 

O'CONNOR,   HENRY.      The  Gas   Engineer's    Pocket 

Book.  Comprising  Tables,  Notes  and  Memoranda;  relating  to  the 
Manufacture,  Distribution  and  Use  of  Coal  Gas  and  the  Construc- 
tion of  Gas  Works.  Second  edition,  revised.  12mo,  full  leather,  gilt 
edges $8.50 

OSBORN,  FRANK  C.     Tables  of  Moments  of  Inertia, 

and  Squares  of  Badii  of  Gyration;  Supplemented  by  others  on  the 
Ultimate  and  Safe  Strength  of  Wrought  Iron  Columns,  Safe  Strength 
of  Timber  Beams,  and  Constants  for  readily  obtaining  the  Shearing 
Stresses,  Beactions,  and  Bending  Moments  in  Swing  Bridges.  12mo, 
leather $3. 00 

OSTERBERG,  MAX.    Synopsis  of  Current  Electrical 

Literature,  compiled  from  Technical  Journals  and  Magazines  during 
1895.  8vo,  cloth $1.00 

OUDIN,  Maurice  A.      Standard  Polyphase  Apparatus 

nnd  Systems.  With  many  diagrams  and  figures.  Third  edition, 
thoroughly  revised.  Fully  Illustrated $3.00 

PAGE,  DAVID.  The  Earth's  Crust,  A  Handy  Out- 
line of  Geology.  16mo,  cloth 75 

PALAZ,  A.,  ScD.  A  Treatise  on  Industrial  Photome- 
try, with  special  application  to  Electric  Lighting.  Authorized  trans- 
lation from  the  French  by  George  W.  Patterson,  Jr.  Second  edition, 
revised.  8vo,  cloth.  Illustrated $4.00 

PARRY,  ERNEST  J.,  B.  Sc.  The  Chemistry  of  Essen- 
tial Oils  and  Artificial  Perfumes.  Being  an  attempt  to  group  together 
the  more  important  of  the  published  facts  connected  with  the  subject ; 
also  giving  an  outline  of  the  principles  involved  in  the  preparation  and 
analysis  of  Essential  Oils.  With  numerous  diagrams  and  tables. 
8vo,  cloth,  illustrated net.  $5.00 


SCIENTIFIC  PUBLICATIONS.  29 


PARRY,  LEONARD  A.,  M.  D.  The  Risks  and  Dan- 
gers of  Various  Occupations  and  their  Prevention.  A  book  that 
should  be  in  the  hands  of  manufacturers,  the  medical  profession, 
sanitary  inspectors,  medical  officers  of  health,  managers  of  works, 
foremen  and  workmen.  8vo,  cloth net.  $3.00 

PARSHALL,  H.  F.,  and  HOB  ART,  H.  M.     Armature 

Windings  of  Electric  Machines.  With  140  full  page  plates,  65  ta- 
bles, and  165  pages  of  descriptive  letter-press.  4to,  cloth $7.50 

PARSHALL,  H.  F.,  and  EVAN  PARRY.     Electrical 

Equipment  of  Tramways (In  Press. ) 

PATERSON,  DAVID,  F.  C.  S.      The  Color  Printing  of 

Carpet  Yarns  ;  a  useful  manual  for  color  chemists  and  textile  printers. 
With  numerous  illustrations.  8vo,  cloth,  illustrated net.  $3.50 

-  Colour  Matching  on  Textiles ;  a  Manual  intended 

for  the  use  of  Dyers,  Calico  Printers  and  Textile  Coloured  Chemists. 
Containing  coloured  frontispiece  and  9  illustrations,  and  14  dyed  pat- 
terns in  appendix.  8vo,  cloth,  illustrated ...  .net,  $3. 03 

The  Science  of  Color  Mixing  ;  a  manual  intended 

for  the  use  of  Dyers,  Calico  Printers  and  Color  Chemists.  With  fig- 
ures, tables  and  colored  plate.  8vo,  cloth,  illustrated net.  $3.00 

PEIRCE,  B.  System  of  Analytic  Mechanics.  4to, 
cloth $10.00 

-  Linear  Associative  Algebra.    New  edition  with  addenda 
and  notes  by  C.  L.  Pierce.     4to,  cloth $4.00 

PERRINE,  F.  A.  C.,  A.  M.,  D.  Sc.  Conductors  for  Elec- 
trical Distribution  ;  Their  Manufacture  and  Materials,  the  Calcula- 
tion of  Circuits,  Pole  Line  Construction,  Underground  Working  and 
other  Uses In  Press. 

PERRY,  JOHN.      Applied  Mechanics.      A  Treatise  for 

the  use  of  students  who  have  time  to  work  experimental,  numerical 
and  graphical  exercises  illustrating  the  subject.  8vo,  cloth,  650 
pages net.  $2.50 

PHILLIPS,    JOSHUA.      Engineering    Chemistry.     A 

Practical  Treatise  for  the  use  of  Analytical  Chemists,  Engineers,  Iron 
Masters,  Iron  Founders,  students  and  others.  Comprising  methods 
of  Analysis  and  Valuation  of  the  principal  materials  used  in  Engin- 
eering works,  with  numerous  Analyses,  Examples  and  Suggestions, 
illustrated."  Third  edition,  revised  and  enlarged.  8vo,  cloth.  .$4.50 

PICKWORTH,  CHAS.  N.      The  Indicator  Hand  Book. 

A  Practical  Manual  for  Engineers.  Part  I.  The  Indicator :  Its 
Construction  and  Application.  81  illustrations.  12mo,  cloth. .  .$1.50 


30  D.  VAN  NOSTRAND  COMPANY'S 


PICKWORTH,   CHAS.  N.     The  Indicator  Handbook. 

Part  II.  The  Indicator  Djagram;  Its  Analysis  and  Calculation. 
With  tables  and  figures.  1'^mo,  cloth,  illustrated $1.50 

The  Slide  Rule.  A  Practical  Manual  of  Instruc- 
tion for  all  Users  of  the  Modern  Type  of  Slide  Rule,  containing  Suc- 
cint  Explanation  of  the  Principle  of  Slide  Rule  Computation,  to- 
gether with  Numerous  Rules  and  Practical  Illustrations,  exhibiting 
the  Application  of  the  Instrument  to  the  Everyday  Work  of  the 
Engineer — Civil,  Mechanical  and  Electrical.  Seventh  edition.  12mo, 
flexible  cloth $1.00 

PLANE  TABLE,  The.  Its  Uses  in  Topographical  Sur- 
veying. From  the  Papers  of  the  United  States  Coast  Survey. 

Illustrated.      8vo,  cloth $2.00 

"This  work  gives  a  description  of  the  Plane  Table  employed  at  the 
United  States  Coast  Survey  office,  and  the  manner  of  using  it." 

PL  ANTE,  GASTON.    The  Storage  of  Electrical  Energy, 

and  Researches  in  the  Effects  created  by  Currents,  combining  Quan- 
tity with  High  Tension.  Translated  irom  the  French  by  Paul  B. 
Elwell.  89  illustrations.  8vo $4.00 

PLATTNER'S  Manual  of  Qualitative  and  Quantitative 

Analysis  with  the  Blow- Pipe.  Eighth  edition,  revised.  Trans- 
lated by  Henry  B.  Cornwall,  E.  M.  Ph.  D..  assisted  by  John  H.  Gas- 
well,  A.  M.  From  the  sixth  German  edition,  by  Prof.  Fried erick 
Kolbeck.  Illustrated  with  87  woodcuts.  4G3  pages.  8vo,  cloth. 
; net,  $4.00 

PLYMPTON,  Prof.  GEO.  W.    The  Aneroid  Barometer : 

Its  Construction  and  Use.      Compiled  from  several  sources.      Eighth 

edition,  revised  and  enlarged.     16mo,  boards,  illustrated $0.50 

Morocco, $1.00 

POCKET  LOGARITHMS,  to  Four  Places  of  Decimals, 

including  Logarithms  of  Numbers,  and  Logarithmic  Sines  and  Tan- 
gents to  Single  Minutes.  To  which  is  added  a  Table  of  Natural 
Sines.  Tangents,  and  Co-Tangents.  16mo,  boards 50 

POPE,  F.  L.  Modern  Practice  of  the  Electric  Tele- 
graph. A  Technical  Hand-Book  for  Electricians,  Managers  and 
Operators.  Fifteenth  edition,  rewritten  and  enlarged,  and  fully 
illustrated.  8vo,  cloth $1.50 

POPPLEWELL,  W.  C.    Elementary  Treatise  on  Heat 

and  Heat  Engines.  Specially  adapted  for  engineers  and  students  of 
engineering.  12mo,  cloth,  illustrated $3.00 

Prevention  of  Smoke,  combined  with  the  Economi- 
cal Combustion  of  Fuel.  With  diagrams,  figures  and  tables.  8vo, 
cloth,  illustrated net,  $3.50 

POWLES,   H.  H.     Steam  Boilers (In  Press.) 


SCIENTIFIC  PUBLICATIONS.  31 


PRAY,  Jr.,  THOMAS.  Twenty  Years  with  the  In- 
dicator; being  a  Practical  Text-Book  for  the  Engineer  or  the  Student, 
with  no  complex  Formulae.  Illustrated.  8vo,  cloth $2.50 

Steam  Tables  and  Engine  Constant.      Compiled 

from  Regnault,  Rankine  and  Dixon  directly,  making  use  of  the  exact 
records.  8vo,  cloth $2.00 

Practical  Compounding  of  Oils,  Tallow  and  Grease,  for 

Lubrication,  etc.,  by  an  Expert  Oil  Refiner.     8vo,  cloth  . .  .net,  $3.50 

PRACTICAL  IRON  FOUNDING.      By  the  author  of 

"Pattern  Making,"  &c.,  &c.  Illustrated  with  over  one  hundred 
engravings.  Third  edition.  12mo,  cloth $1.50 

PREECE,  W.  H.    Electric  Lamps (In  Press.) 

PRELINI,  CHARLES.,  C.   E.  Tunneling;   a  Practical 

Treatise  containing  149  \Vorkiug  Drawings  and  Figures.  With  addi- 
tions by  Charles  S.  Hill,  C.  E.,  Associate  Editor  "Engineering 
News."  311  pages.  Second  edition,  revised.  8vo,  cloth,  illustrated. 
$3. 00 

PREECE,  W.  H.,  and  STUBBS,  A.  T.  Manual  of  Tele- 
phony. Illustrations  and  plates.  12mo,  cloth $4.50 

PREMIER  CODE.     (See  Hawke,  Wm.  H.) 

PRESCOTT,  Prof.  A.  B.    Organic  Analysis.    A  Manual 

of  the  Descriptive  and  Analytical  Chemistry  of  certain  Carbon  Com- 
pounds in  Common  Use  ;  a  Guide  in  the  Qualitative  and  Quantitative 
Analysis  of  Organic  Materials  in  Commercial  and  Pharmaceutical 
Assays,  in  the  estimation  of  Impurities  under  Authorized  Standards, 
and  in  Forensic  Examinations  for  Poisons,  with  Directions  for  Ele- 
mentary Organic  Analysis.  Fifth  edition.  8vo,  cloth $5.00 

-  Outlines   of  Proximate  Organic  Analysis,  for  the 

Identification,  Separation,  and  Quantitative  Determination  of  the 
more  commonly  occurring  Organic  Compounds.  Fourth  edition. 
12mo,  cloth $1.75 

PRESCOTT,  A.  B.,  and  E.  C.  SULLIVAN.  (Univers- 
ity of  Michigan).  First  Book  in  Qualitative  Chemistry.  For  Studies 
of  Water  Solution  and  Mass  Action.  Eleventh  edition,  entirely  re- 
written. 12mo,  cloth net,  $1.50 

-  and  OTIS  COE  JOHNSON.      Qualitative  Chemical 

Analysis.  A  Guide  in  the  Practical  Study  of  Chemistry  and  in  the 
work  of  Analysis.  Fifth  revised  and.  enlarged  edition,  entirely  re- 
written. With  Descriptive  Chemistry  extended  throughout.. net  $3.50 

PRITCHARD,    O.    G.      The    Manufacture    of  Electric 

Light  Carbons.     Illustrated.     8vo,  paper , 60 


32  D.  VAN  NOSTRAND  COMPANY'S 


PULLEN,  W.  W.  F.     Application  of  Graphic  Methods 

to  the  Design  of  Structures.  Specially  prepared  for  the  use  of  En- 
gineers. A  Treatment  by  Graphic  Methods  of  t!  e  Forces  and  Princi- 
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RANDAU,    PAUL.       Enamels    and   Enamelling;    an 

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RANKINE,  W.  J.  MACQUORN.     Applied  Mechanics. 

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SCIENTIFIC  PUBLICATIONS.  33 


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34  D.  VAN  NOSTRAND  COMPANY'S 


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SCIENTIFIC  PUBLICATIONS.  35 


ROSE,  JOSHUA,  M.E.  The  Pattern-Makers'  Assistant. 

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SAELTZER,  ALEX.  Treatise  on  Acoustics  in  connec- 
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SCHELLEN,  Dr.  H.  Magneto-Electric  and  Dynamo- 
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SCHUMANN,  F.  A  Manual  of  Heating  and  Ventilation 

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36  D.  VAN  NOSTRAND  COMPANY'S 


SCIENCE  SERIES,  The  Van  Nostrand.  [See  List,  p.  46] 

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SEATON,  A.   E.    A  Manual  of  Marine  Engineering. 

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SCIENTIFIC  PUBLICATIONS.  37 


SHIELDS,  J.  E.   Notes  on  Engineering  Construction. 

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of  the  Material  employed  in  Tunnelling,  Bridging,  Canal  and  Road 
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SHUNK,  W.  F.   The  Field  Engineer.    A  Handy  Book 

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SMITH,  ISAA.C  W.,  C.E.      The  Theory  of  Deflections 

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38  D.  VAN  NOSTRAND  COMPANY'S 


SPANG,  HENRY  W.  A  Practical  Treatise  on  Light- 
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SPEYERS,   CLARENCE  L.    Text  Book  of  Physical 

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STAHL,  A.  W.,  and  A.  T.  WOODS.  Elementary  Me- 
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STALEY,  CADY,  and  PIERSON,  GEO.  S.  The  Separ- 
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STEWART,  R.  W.    A  Text  Bo9k  of  Light.    Adapted 

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STILES,  AMOS.   Tables  for  Field  Engineers.   Designed 

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SCIENTIFIC  PUBLICATIONS.  39 


STONEY,   B.  D.    The  Theory  of  Stresses  in  Girders 

and  Similar  Structures.  With  observations  on  the  application  of 
Theory  to  Practice,  and  Tables  of  Strength,  and  other  properties  of 
Materials.  New  revised  edition,  with  numerous  additions  on  Graphic 
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STUART,  C.  B.  TJ.  S.  N.      Lives  and  Works  of  Civil 

and  Military  Engineers  of  America.  With  10  steel-plate  engravings. 
8vo,  cloth $5.00 

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Illustrated  with  24  fine  Engravings  on  Steel.  Fourth  edition.  4to, 
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SUFFICING,    E.    R.      Treatise    on    the  Art  of  Glass 

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lustrated  net,  $3.50 

SWEET,  S.  H.     Special  Report  on  Coal,  showing  its 

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the  Atlantic  Coast.  With  maps.  8vo,  cloth $3.00 

SWINTON,  ALAN  A.  CAMPBELL.    The  Elementary 

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SWOOPE,  C.  WALTON.  Practical  Lessons  in  Elec- 
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large  instruction  plates.  8vo,  cloth,  illustrated.  Third  edition. 
net,  $2.00 

TAILFER,  L.     Practical  Treatise  on  the  Bleaching  of 

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illustrated $5.00 

TEMPLETON,  WM.  The  Practical  Mechanic's  Work- 
shop Companion.  Comprising  a  great  variety  of  the  most  useful 
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THOM,  CHAS.,  and  WILLIS  H.  JONES.     Telegraphic 

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THOMPSON,  EDWARD  P.,  M.  E.     How  to  Make  In- 

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for  Inventors.  Second  edition.  8vo,  boards $1.00 


40  D.  VAN  NOSTRAND  COMPANY'S 


THOMPSON,   EDWARD  P.,   M.    E.      Roentgen  Rays 

and  Phenomena  of  the  Anode  and  Cathode.  Principles,  Applications 
and  Theories.  For  Students,  Teachers,  Physicians,  Photographers, 
Electricians  and  others.  Assisted  by  Louis  M.  Pignolet,  N.  D.  C. 
Hodges,  and  Ludwig  Gutmann,  E.  E.  With  a  Chapter  on  Generali- 
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By  Professor  Wm.  Anthony.  50  Diagrams,  40  Half-tones.  8vo, 
cloth $1.50 

THORNLEY,  T.      Cotton  Combing  Machines.     With 

numerous  tables,  engravings  and  diagrams.      8vo,  cloth,  illustrated. 

343  pages $3.00 

Contents. — Preface,  List  of  Illustrations ;  The  Silver  Lap  Ma- 
chine ;  Ribbon  Lap  Machine  and  Draw-Frame  ;  General  Description 
of  the  Heilmann  Comber ;  The  Cam  Shaft ;  The  Detaching  and  At- 
taching Mechanism  of  the  Comber ;  The  Duplex  Comber ;  Re-setting 
of  Combers  ;  The  erection  of  a  Heilmann  Comber ;  Stop  Motions  ; 
Various  Calculations  ;  Various  Notes  and  Discussions  ;  Cotton  Comb- 
ing Machines  of  Continental  Make  ;  Index. 

TODD,  JOHN  and  W.  B.  WHALL.  Practical  Seaman- 
ship for  Use  in  the  Merchant  Service  :  Including  all  ordinary  sub- 
jects ;  also  Steam  Seamanship,  Wreck  Lifting,  Avoiding  Collision, 
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by  seamen  of  the  present  day.  Second  edition,  with  247  illustrations 
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TOOTHED  GEARING.       A  Practical  Hand-Book  for 

Offices  and  Workshops.  By  a  Foreman  Patternmaker.  184  Illustra- 
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TRATMAN,   E.   E.   RUSSELL.     Railway  Track  and 

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TRAVERSE  TABLES,  showing  the  difference  of  Lati- 
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Scribner's  Pocket  Table  Book.  16mo,  boards.  (Van  Nostrand's 
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TRE VERT,  EDWARD.    How  to  build  Dynamo-Electric 

Machinery,  embracing  Theory  Designing  and  Construction  of  Dy- 
namos and  Motors.  With  appendices  on  Field  Magnet  and  Armature 
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TUCKER,  Dr.  J.  H.  A  Manual  of  Sugar  Analysis,  in- 
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Sugar,  Dextrose,  Levulose,  and  Milk  Sugar.  8vo,  cloth,  illus- 
trated  $3.50 


SCIENTIFIC  PUBLICATIONS.  41 


TUMLIRZ,  Dr.  O.      Potential  and  its  Application  to 

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lated from  the  German  by  D.  Eobertson.  HI.  12mo,  cloth $1.25 

TUNNER,  P.      A.    Treatise  on    Roll-Turning  for  the 

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the  Pennsylvania  Steel  Works,  with  numerous  engravings,  woodcuts. 
8vo,  cloth,  with  folio  atlas  of  plates $10.00 

URQUHART,  J.  W.  Electric  Light  Fitting.  Embody- 
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Working  Electrical  Engineers.  With  numerous  illustrations.  12mo, 
cloth $2.00 

Electro-Plating.      A   Practical  Hand  Book  on  the 

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—  Electrotyping ;  A  Practical  Manual  forming  a  New 

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TJRQUHART,  J.  W.  Dynamo  Construction:  a  Practi- 
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VAN  NOSTRAND'S  Engineering  Magazine.  Com- 
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VAN  WAGENEN,  T.  F.  Manual  of  Hydraulic  Mining. 

For  the  Use  of  the  Practical  Miner.  Hevised  and  enlarged  edition. 
18mo,  cloth $1.00 

VILLON,  A.  M.      Practical  Treatise  on  the  Leather 

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42  D.  VAN  NOSTBAND  COMPANY'S 


VON  GEORGIEVICS,  GEORG.    Chemical  Technology 

of  Textile  Fibres  ;  Their  Origin,  Structure,  Preparation,  Washing, 
Bleaching,  Dyeing,  Printing,  and  Dressing.  Translated  from  the 
German  by  Charles  Salter.  With  many  diagrams  and  figures.  8vo, 

cloth,  illustrated.     306  pages $4.50 

Contents.—  The  Textile  Fibres  ;  Washing,  Bleaching  and  Carbon- 
izing ;  Mordants  and  Mordanting  ;  Dyeing,  Printing,  Dressing  and 
Finishing;  Index. 

WALKER,  W.  H.     Screw  Propulsion.    Notes  on  Screw 

Propulsion,  its  Rise  and  History.     8vo,  cloth 75 

WALKER,   SYDNEY  F.      Electrical  Engineering  in 

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trical Apparatus.  Third  edition,  revised,  with  numerous  illustra- 
tions   $2.00 

Electric  Lighting  for  Marine  Engineers,  or  How  to 

Light  a  Ship  by  the  Electric  Light  and  How  to  Keep  the  Apparatus 
in  Order.  103  illustrations.  8vo,  cloth.  Second  edition $2.00 

WALLIS-TAYLER,  A.  J.  Modern  Cycles,  A  Practi- 
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tions. 8vo,  cloth $4.00 

Motor    Cars,   or   Power    Carriages    for    Common 


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Bearings  and  Lubrication.      A  Handbook  for  every 

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Refrigeration  and  Cold  Storage  ;  being  a  complete 

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361  diagrams  and  figures.     8vo,  cloth,  illustrated net,  $4.50 

Sugar  Machinery.    A  Descriptive  Treatise,  devoted 

to  the  Machinery  and  Apparatus  used  in  the  Manufacture  of  Cane 
and  Beet  Sugars.     12mo,  cloth,  ill $2.00 

WANKLYN,  J.  A.  A  Practical  Treatise  on  the  Exam- 
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12mo,  cloth $1.00 

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WANSBROUGH,  WM.  D.  The  A.  B.  C.  of  the  Differ- 
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ise on  Steam,  and  its  application  to  the  Useful  Arts,  especially  to 
Navigation.  8vo,  cloth $1.00 


SCIENTIFIC  PUBLICATIONS.  43 


WARING,  GEO.  E.,  Jr.    Sewerage  and  Land  Drainage. 

Illustrated  with  wood-cuts  in  the  text,  and  full-page  and  folding 
plates.  Quarto.  Cloth.  Third  edition $6.00 

Modern  Methods  of  Sewage  Disposal  for  Towns", 

Public  Institutions  and  Isolated  Houses.  Second  edition,  revised 
and  enlarged.  260  pages.  Illustrated,  cloth..... $2.00 

—  How  to  Drain  a  House.     Practical  Information  for 

Householders.     Third  edition  enlarged.     12mo,  cloth $1.25 

WATSON,  E.  P.  Small  Engines  and  Boilers.  A  man- 
ual of  Concise  and  Specific  Directions  for  the  Construction  of  Small 
Steam  Engines  and  Boilers  of  Modern  Types  from  five  Horse-power 
down  to  model  sizes.  Illustrated  with  Numerous  Diagrams  and  Half 
Tone  Cuts.  12mo,  cloth $1.25 

WATT,  ALEXANDER.  Electro-Deposition.  A  Prac- 
tical Treatise  on  the  Electrolysis  of  Gold,  Silver,  Copper,  Nickel,  and 
other  Metals,  with  Descriptions  of  Voltaic  Batteries,  Magneto  and 
Dynamo-Electric  Machines,  Thermopiles,  and  of  the  Materials  and 
Processes  used  in  every  Department  of  the  Art,  and  several  chapters 
on  Electro-Metallurgy.  With  numerous  illustrations.  Third  edition, 
revised  and  corrected.  New  and  enlarged  edition In  Press. 

Electro-Metallurgy  Practically  Treated.      Eleventh 

edition,  considerably  enlarged.     12mo,  cloth $1.00 

-  The  Art  of  Soap-Making.    A  Practical  Handbook 

of  the  Manufacture  of  Hard  and  Soft  Soaps,  Toilet  Soaps,  &c.  In- 
cluding many  New  Processes,  and  a  Chapter  on  the  Recovery  of 
Glycerine  from  Waste  Lyes.  With  illustrations.  Fifth  edition, 
revised  and  enlarged.  8vo,  cloth $3.00 

WATT,  ALEXANDER.  The  Art  of  Leather  Manufact- 
ure. Being  a  Practical  Handbook,  in  which  the  Operations  of  Tan- 
ning, Currying,  and  Leather  Dressing  are  Fully  Described,  and  the 
Principles  of  Tanning  Explainad,  and  many  Recent  Processes  Intro- 
duced. With  numerous  illustrations.  Second  edition.  8vo,  cl.$4.00 

WE  ALE,   JOHN.     A  Dictionary    of  Terms  Used   in 

Architecture,  Building,  Engineering,  Mining,  Metallurgy,  Archaelogy, 
the  Fine  Arts,  etc. ,  with  explanatory  observations  connected  with 
applied  Science  and  Art.  fifth  edition,  revised  and  corrected. 
12mo,  cloth $2.50 

WEBB,   HERBERT  LAWS.      A  Practical    Guide   to 

the  Testing  of  Insulated  Wires  and  Cables.  Illustrated.  12mo, 
cloth $1.00 

-  The  Telephone  Hand  Book.       128  illustrations.      146 
pages.     16mo. ,    cloth $1. 00 

WEEKES,  R.   W.    The   Design  of  Alternate  Current 

Transformers.     Illustrated.     12mo,  cloth $1.00 


44  D.  VAN  NOSTBAND  COMPANY'S 


WEISBACH,    JULIUS.     A    Manual    of    Theoretical 

Mechanics.  Ninth  American  edition.  Translated  from  the  fourth 
augmented  and  improved  German  edition,  with  an  Introduction  to 
the  Calculus  by  Eckley  B.  Coxe,  A.M.,  Mining  Engineer.  1,100 

pages,  and  902  woodcut  illustrations.     8vo,  cloth $6.00 

Sheep 7.50 

WESTON,    EDMUND  B.      Tables    Showing   Loss  of 

Head  Due  to  Friction  of  Water  in  Pipes.  Second  edition.  12mo, 
cloth $1.50 

WEYMOUTH,   F.   MARTEN.      Drum  Armatures  and 

Commutators.  (Theory  and  Practice.)  A  complete  Treatise  on  the 
Theory  and  Construction  of  Drum  Winding,  and  of  commutators  for 
closed-coil  armatures,  together  with  a  full  resume  of  some  of  the  prin- 
cipal points  involved  in  their  design,  and  an  exposition  of  armature 
re-actions  and  sparking.  8vo,  cloth $3.00 

WHEELER,  Prof,  J.  B.      Art  of  War.      A  Course  of 

Instruction  in  the  Elements  of  the  Art  and  Science  of  War,  for  the 
Use  of  the  Cadets  of  the  United  States  Military  Academy,  West  Point, 
N.  Y.  12mo,  cloth $1.75 

Field    Fortifications.      The    Elements    of  Field 

Fortifications,  for  the  Use  of  the  Cadets  of  the  United  States  Military 
Academy,  West  Point,  N.  Y.  12mo,  cloth $1.75 

WHIPPLE,   S.,  C.  E.      An  Elementary  and  Practical 

Treatise  on  Bridge  Building.      8vo,  cloth $3.00 

WHITE,  W.  H.,  K.  C.  B.  A  Manual  of  Naval  Archi- 
tecture, for  use  of  Officers  of  the  Royal  Navy,  Officers  of  the  Merchan- 
tile  Marine,  Yachtsmen,  Shipowners  and  Shipbuilders.  Containing 
many  figures,  diagrams  and  tables.  Thick,  8vo,  cloth,  illus $9.00 

WILKINSON,  H.  D.  Submarine  Cable-Laying,  Re- 
pairing and  Testing.  8vo,  cloth $5.00 

WILLIAMSON,  R.  S.    On  the  Use  of  the  Barometer  on 

Surveys  and  Beconnoissances.  Part  I.  Meteorology  in  its  Connection 
with  Hypsometry.  Part  II.  Barometric  Hypsometry.  With  Illus- 
trative tables  and  engravings.  4to,  cloth $15.00 

Practical  Tables  in  Meteorology  and  Hypsometry, 

in  connection  with  the  use  of  the  Barometer.     4to,  cloth $2.50 

WILSON,  GEO.  Inorganic  Chemistry,  with  New  No- 
tation. Be  vised  and  enlarged  by  H.  G.  Madan.  New  edition. 
12mo,  cloth $2.00 

WINKLER,  CLEMENS.  Handbook  of  Technical  Gas- 
Analysis.  With  figures  and  diagrams.  Second  English  Edition, 
Translated  from  the  Third,  greatly  enlarged  German  Edition,  with 
some  additions  by  George  Lunge,  Ph.  D.  8vo,  cloth,  illustrated,  190 
pages $4. 00 


SCIENTIFIC  PUBLICATIONS.  45 


WOODBURY,  D.  V.    Treatise  on  the  Various  Elements 

of  Stability  in  the  Weil-Proportioned  Arch.    8vo,  half  morocco.. $4. 00 

WRIGHT,  T.  W.?  PR.OF.  (Union  College).  Elements  of 
Mechanics ;  including  Kinematics,  Kinetics  and  Statics.  With  ap- 
plications. Third  edition,  revised  and  enlarged.  8vo,  cloth. .  $2.50 

WYLIE,  CLAUDE.  Iron  and  Steel  Founding.  Illus- 
trated with  39  diagrams.  Second  edition,  revised  and  enlarged. 
8vo,  cloth $2.00 

WYNKOOP,    RICHARD.      Vessels  and   Voyages,   as 

Regulated  by  Federal  Statutes  and  Treasury  Instructions  and  Decis- 
ions. 8vo,  cloth $2.00 

YOUNG,  J.  ELTON.      Electrical  Testing  for  Telegraph 

Engineers.  With  Appendices  consisting  of  Tables.  8vo,  cloth,  illus- 
trated  $4.00 

YOUNG     SEAMAN'S     MANUAL.       Compiled   from 

Various  Authorities,  and  Illustrated  with  Numerous  Original  and 
Select  Designs,  for  the  Use  of  the  United  States  Training  Ships  and 
the  Marine  Schools.  8vo,  half  roan $3.00 

ZIPSER,    JULIUS.       Textile    Raw    Materials,    and 

their  Conversion  into  Yarns.  The  study  of  the  Eaw  Materials  and 
the  Technology  of  the  Spinning  Process.  A  Text-book  for  Textile, 
Trade  and  higher  Technical  Schools,  as  also  for  self -instruction. 
Based  upon  the  ordinary  syllabus  and  curriculum  of  the  Imperial  and 
Royal  Weaving  Schools.  Translated  from  the  German  by  Chas.  Sal- 
ter.  8vo,  cloth,  illustrated $5.00 


Catalogue  of  the  Van  Nostrand 

Science  Series. 


Y  are  put  up  in  a  uniform,  neat,  and  attractive  form. 
J-      boards.     Price  30  cents  per  volume.      The   subjects  are  of  an 
eminently  scientific  character,  and  embrace  a  wide  range  of  topics,  and 
are  amply  illustrated  when  the  subject  demands. 

No.  i.  CHIMNEYS  FOR  FURNACES  AND  STEAM-BOILERS. 
By  R.  Armstrong,  C.E.  Third  American  edition,  revised  and  partly 
rewritten,  with  an  appendix  on  Theory  of  Chimney  Draught,  by  F.  E. 
Idell,  M.E. 

No.  2.     STEAM-BOILER  EXPLOSIONS.    By  Zerah  Colburn.     New 
edition,  revised  by  Prof.  R.  H.  Thurston. 


No.  3.     PRACTICAL    DESIGNING     OF     RETAINING- WALLS. 

By 

W.  Cain. 


Arthur  Jacob,  A.B.     Second  edition,  revised,  with  additions  by  Prof. 


No.  4.  PROPORTIONS  OF  PINS  USED  IN  BRIDGES.  Second 
edition,  with  appendix.  By  Charles  E.  Bender,  C.E. 

No.  5.  VENTILATION  OF  BUILDINGS.  By  W.  F.  Butler.  Second 
edition,  re-edited  and  enlarged  by  James  L.  Greenleaf,  C.E. 

No.  6.     ON     THE     DESIGNING     AND     CONSTRUCTION      OF 

STORAGE   RESERVOIRS.     By  Arthur  Jacob,  A.B.     Second  edition, 
revised,  with  additions  by  E.  Sherman  Gould. 

No.  7.  SURCHARGED  AND  DIFFERENT  FORMS  OF  RE- 
TAINING-WALLS.  By  James  S.  Tate,  C.E. 

No.  8.  A  TREATISE  ON  THE  COMPOUND  ENGINE.  By  John 
Turnbull,  jun.  Second  edition,  revised  by  Prof.  S.  W.  Robinson. 

No.  9.  A  TREATISE  ON  FUEL.  By  Arthur  V.  Abbott,  C.  E. 
Founded  on  the  original  treatise  of  C.  William  Siemens,  D.C.L. 

No.  10.  COMPOUND  ENGINES.  Translated  from  the  French  of  A. 
Mallet.  Second  edition,  revised,  with  Results  of  American  Practice,  by 
Richard  H.  Buel,  C.E. 

No.  ii.     THEORY  OF  ARCHES.     By  Prof.  W.  Allan. 

No.  12.  A  THEORY  OF  VOUSSOIR  ARCHES.  By  Prof.  W.  E. 
Cain.  Second  edition,  revised  and  enlarged.  Illustrated. 

No.  13.  GASES  MET  WITH  IN  COAL-MINES.  By  J.  J.  Atkinson. 
Third  edition,  revised  and  enlarged  by  Edward  H  Williams,  jun. 


D.   VAN  NOSTRAND  COMPANY'S 


No.  14.     FRICTION  OF  AIR  IN  MINES.     By  J.  J.  Atkinson. 

No.  15.     SKEW  ARCHES.     By  Prof.  E.  W.  Hyde,  C.E.    Illustrated. 

No.  16.  A  GRAPHIC  METHOD  OF  SOLVING  CERTAIN  QUES- 
TIONS IN  ARITHMETIC  OR  ALGEBRA.  By  Prof.  Geo.  L.  Vose. 

No.  17.  WATER  AND  WATER-SUPPLY.  By  Prof.  W.  H.  Corfield 
of  the  University  College,  London. 

No.  18.    SEWERAGE    AND     SEWAGE    PURIFICATION.      By 

M.  N.  Baker,  Assoc.  Ed.  Engineering  News. 

No.  19.     STRENGTH     OF      BEAMS      UNDER      TRANSVERSE 

LOADS.     By  Prof.  W.  Allan,  author  of  "Theory  of  Arches." 

No.  20.  BRIDGE  AND  TUNNEL  CENTRES.  By  John  B.  Me- 
Master,  C.E. 

No.  21.     SAFETY  VALVES.     By  Richard  H.  Buel,  C.E.  Third  edition. 
No,  22.     HIGH    MASONRY    DAMS.     By  E.  Sherman  Gould,  C.E. 

No.  23.  THE  FATIGUE  OF  METALS  UNDER  REPEATED 

STRAINS.  With  Various  Tables  of  Results  and  Experiments.  From 
the  German  of  Prof.  Ludwig  Spangenburgh,  with  a  Preface  by  S.  H. 
Shreve,  A.M. 

No.  24.  A  PRACTICAL  TREATISE  ON  THE  TEETH  OP 

WHEELS.     By  Prof.  S.  W.  Robinson.     Second  edition,  revised. 

No.  25.  ON  THE  THEORY  AND  CALCULATION  OF  CON- 
TINUOUS BRIDGES.  By  R.  M.  Wilcox,  Ph.B. 

No.  26.     PRACTICAL    TREATISE  ON    THE    PROPERTIES  OF 

CONTINUOUS    BRIDGES      By  Charles  Bender,  C.E. 

No.  27.     ON     BOILER     INCRUSTATION      AND     CORROSION 

By  F.  J.  Rowan.     New  edition,  revised  and  partly  rewritten  by  F.  E. 
Idell,  M.  E. 

No.  28.  TRANSMISSION  OF  POWER  BY  WIRE  ROPES 
By  Albert  W.  Stahl,  U.S.N.  Second  edition. 

No.  29.  STEAM  INJECTORS.  Translated  from  the  French  ot 
M.  Leon  Pochet. 

No.  30.  TERRESTRIAL  MAGNETISM,  AND  THE  MAGNET- 
ISM  OF  IRON  VESSELS.  By  Prof.  Fairman  Rogers. 

No.  31.  THE  SANITARY  CONDITION  OF  DWELLING- 
HOUSES  IN  TOWN  AND  COUNTRY.  By  George  E.  Waring,  jua 

No.  32.  CABLE-MAKING  FOR  SUSPENSION  BRIDGES.  By 
W.  Hildenbrand,  C.E. 

No.  33.  MECHANICS  OF  VENTILATION.  By  George  W.  Rafter, 
C.E*.  New  edition  (1895),  revised  by  author. 

No.  34.  FOUNDATIONS.  By  Prof.  Jules  Gaudard,  C.E.  Translated 
from  the  French. 

No.  35.  THE  ANEROID  BAROMETER:  ITS  CONSTRUC- 
TION AND  USE.  Compiled  by  George  W.  Plympton.  Eighth  edition. 

No.  36.     MATTER    AND    MOTION,      By  J.  Clerk   Maxwell,    M.A. 
Second  American  edition. 


SCIENCE  SERIES. 


No.  37.  GEOGRAPHICAL  SURVEYING:  ITS  USES,  METH- 
ODS, AND  RESULTS.  By  Frank  De  Yeaux  Carpenter,  C.E. 

No.  38.    MAXIMUM    STRESSES    IN    FRAMED    BRIDGES.     By 

Prof.  William  Cain,  A.M.,  C.E.    New  and  revised  edition. 

No.  39.    A      HANDBOOK      OF      THE      ELECTRO-MAGNETIC 

TELEGRAPH.     By  A.  E.  Loring.    New  enlarged  edition. 

No.  40.     TRANSMISSION  OF  POWER  BY  COMPRESSED  AIR. 

By  Robert  Zahner,  M.E.    Second  edition. 

No.  41.  STRENGTH  OF  MATERIALS.  By  William  Kent,  C.E., 
Assoc.  Ed.  Engineering  News. 

No.  42.  THEORY  OF  STEEL-CONCRETE  ARCHES  AND 

OF  VAULTED  STRUCTURES.     By  Prof.  William  Cain. 

No.  43.  WAVE  AND  VORTEX  MOTION.  By  Dr.  Thomas  Craig  of 
Johns  Hopkins  University. 

No.  44.  TURBINE  WHEELS.  By  Prof.  W.  P.  Trowbridge,  Columbia 
College.  Second  edition. 

No.  45.  THERMODYNAMICS.  By  Prof.  H.  T.  Eddy,  University  of 
Cincinnati. 

No.  46.  ICE-MAKING  MACHINES.  New  edition,  revised  and  en- 
larged by  Prof.  J.  E.  Denton.  From  the  French  of  M.  Le  Doux. 

No.  47.    LINKAGES;    THE    DIFFERENT   FORMS   AND  USES 

OF  ARTICULATED  LINKS.    By  J.  D.  C.  de  Roos. 

No.  48.     THEORY    OF     SOLID    AND    BRACED    ARCHES.      By 

William  Cain,  C.E. 

No.  49.     ON    THE    MOTION    OF    A    SOLID   IN    A    FLUID.     By 

Thomas  Craig,  Ph.D. 

No.  50.  DWELLING-HOUSES  :  THEIR  SANITARY  CON- 
STRUCTION AND  ARRANGEMENTS.  By  Prof.  W.  H.  Corfield. 

No.  51.     THE    TELESCOPE  :    ITS    CONSTRUCTION,   ETC.    By 

Thomas  Nolan. 

No.  52.  IMAGINARY  QUANTITIES.  Translated  from  the  French  of 
M.  Argand.  By  Prof.  Hardy. 

No.  53.     INDUCTION  COILS  :   HOW  MADE  AND  HOW  USED. 

Third  American,  from  Ninth  English  edition. 

No.  54.  KINEMATICS  OF  MACHINERY.  By  Prof.  Kennedy.  With 
an  introduction  by  Prof.  R.  H.  Thurston. 

No.  55.     SEWER  GASES  :  THEIR  NATURE  AND  ORIGIN.     By 

A.  de  Varona. 

No.  56.  THE  ACTUAL  LATERAL  PRESSURE  OF  EARTH- 
WORK. By  Benjamin  Baker,  M.  Inst  C.E. 

No.  57.  INCANDESCENT  ELECTRIC  LIGHTING.  A  Practical 
Description  of  the  Edison  System.  By  L.  H.  Latimer,  to  which  is 
added  the  Design  and  Operation  of  Incandescent  Stations,  by  C.  J. 
Field,  and  the  Maximum  Efficiency  of  Incandescent  Lamps,  by  John 
W.  Howell. 

No.  58.  THE  VENTILATION  OF  COAL-MINES.  By  W.  Fairley. 
M.E  ,  F.S.S. 


D.   VAN  NOSTRAND  COMPANY'S 


No.  59.  RAILROAD  ECONOMICS;  OR,  NOTES,  WITH  COM- 
MENTS. By  S.  W.  Robinson,  C.E. 

No.  60.     STRENGTH    OF    WROUGHT-IRON     BRIDGE     MEM- 

BERS.     By  S.  W.  Robinson,  C.E. 

No.  61.  POTABLE  WATER  AND  METHODS  OF  DETECT- 
ING IMPURITIES.  By  M.  N.  Baker,  Ph.B. 

No.  62.  THE  THEORY  OF  THE  GAS-ENGiNE.  By  Dugald  Clerk. 
Second  edition.  With  additional  matter.  Edited  by  F.  E.  Idell,  M.E. 

No.  63.  HOUSE  DRAINAGE  AND  SANITARY  PLUMBING. 

By  W.  P.  Gerhard.     Eighth  edition,  revised. 

No.  64.     ELECTRO-MAGNETS.  By  A.  N.  Mansfield,  S.B. 

No.  65.  POCKET  LOGARITHMS  TO  FOUR  PLACES  OF  DECI- 
MALS. 

No.  66.  DYNAMO-ELECTRIC  MACHINERY.  By  S.  P.  Thompson 
With  notes  by  F.  L.  Pope.  Third  edition. 

No.  67.    HYDRAULIC      TABLES      BASED      ON      "KUTTER'S 

FORMULA."     By  P.  J.  Flynn. 

No.  68.  STEAM-HEATING.  By  Robert  Briggs.  Third  edition,  revised, 
with  additions  by  A.  R.  Wolff. 

No.  69.  CHEMICAL  PROBLEMS.  By  Prof.  J.  C.  Foye.  Fourth 
edition,  revised  and  enlarged. 

No.  70.  EXPLOSIVE  MATERIALS.  The  Phenomena  and  Theories 
of  Explosion,  and  the  Classification,  Constitution  and  Preparation  of 
Explosives.  By  First  Lieut.  John  P.  Wisser,  U.S.A. 

No.  71.  DYNAMIC  ELECTRICITY.  By  John  Hopkinson,  J.  N. 
Shoolbred,  and  R.  E.  Day. 

No.  72.  TOPOGRAPHICAL  SURVEYING.  By  George  J.  Specht, 
Prof.  A.  S.  Hardy,  John  B.  McMaster,  and  H.  F.  Walling. 

No.  73.  SYMBOLIC  ALGEBRA;  OR,  THE  ALGEBRA  OF 

ALGEBRAIC  NUMBERS.     By  Prof.  W.  Cain. 

No.  74.  TESTING  MACHINES  :  THEIR  HISTORY,  CON- 
STRUCTION, AND  USE.  By  Arthur  V.  Abbon. 

No.  75.  RECENT  PROGRESS  IN  DYNAMO-ELECTRIC  MA- 
CHINES. Being  a  Supplement  to  Dynamo-Electric  Machinery.  By 
Prof.  Sylvanus  P.  Thompson. 

No.  76.  MODERN  REPRODUCTIVE  GRAPHIC  PROCESSES. 

By  Lieut.  James  S.  Pettit,  U.S.A. 

No.  77.  STADIA  SURVEYING.  The  Theory  ot  Stadia  Measurements. 
By  Arthur  Winslow. 

No.  78.  THE  STEAM-ENGINE  INDICATOR,  AND  ITS  USE 
By  W.  B.  Le  Van. 

No.  79.     THE  FIGURE  OF  THE  EARTH.     By  Frank  C.  Roberts,C.E. 

No.  80.  HEALTHY  FOUNDATIONS  FOR  HOUSES.  By  Glen* 
Brown. 


SCIENCE  SERIES. 


No.  81.     WATER      METERS  :       COMPARATIVE      TESTS     OF 

ACCURACY,  DELIVERY,   ETC.     Distinctive  features  of  the  Worth- 
ington,  Kennedy,  Siemens,  and  Hesse  meters.     By  Ross  E.  Browne. 

No.  82.     THE    PRESERVATION    OF    TIMBER    BY    THE   USE 
OF  ANTISEPTICS.     By  Samuel  Bagster  Boulton,  C.E. 


33.     MECI 
Shaw,  C.E. 


No.  84.  FLOW  OF  WATER  IN  OPEN  CHANNELS,  PIPES, 
CONDUITS,  SEWERS,  ETC.  With  Tables.  By  P.  J.  Flynn,  C.E. 

No.  85.     THE  LUMINIFEROUS  AETHER.     By  Prof,  de  Volson  Wood. 

No.  86.     HAND-BOOK  OF  MINERALOGY;  DETERMINATION 

AND  DESCRIPTION  OF  MINERALS  FOUND  IN  THE  UNITED 
STATES.     By  Prof.  J.  C.  Foye. 

No.  87.     TREATISE     ON      THE      THEORY     OF      THE     CON- 

STRUCTION   OF   HELICOIDAL    OBLIQUE   ARCHES.     By  John 
L.  Culley,  C.E. 

No.  88.  BEAMS  AND  GIRDERS.  Practical  Formulas  for  their  Re- 
sistance.  By  P.  H.  Philbrick. 

No.  89.     MODERN       GUN-COTTON  :      ITS      MANUFACTURE, 

PROPERTIES,  AND  ANALYSIS.     By  Lieut.  John  P.  Wisser,  U.S.A. 

No.  90.  ROTARY  MOTION,  AS  APPLIED  TO  THE  GYRO- 
SCOPE. By  Gen.  J.  G.  Barnard. 

No.  91.  LEVELING:  BAROMETRIC,  TRIGONOMETRIC,  AND 
SPIRIT.  By  Prof.  I.  O.  Baker. 

No.  92.     PETROLEUM  :     ITS     PRODUCTION     AND     USE.      By 

Boverton  Redwood,  F.I.C.,  F.C.S. 

No.  93.  RECENT  PRACTICE  IN  THE  SANITARY  DRAIN- 
AGE OF  BUILDINGS.  With  Memoranda  on  the  Cost  of  Plumbing 
Work.  Second  edition,  revised.  By  William  Paul  Gerhard,  C.  E. 

No.  94.  THE  TREATMENT  OF  SEWAGE.  By  Dr.  C.  Meymott 
Tidy. 

No.  95.  PLATE  GIRDER  CONSTRUCTION.  By  Isami  Hiroi,  C.E. 
Second  edition,  revised  and  enlarged.  Plates  and  Illustrations. 

No.  96.  ALTERNATE  CURRENT  MACHINERY.  By  Gisbert 
Kapp,  Assoc.  M.  Inst.,  C.E. 

No.  97.     THE    DISPOSAL    OF    HOUSEHOLD   WASTE.     By  W. 

Paul  Gerhard,  Sanitary  Engineer. 

No.  98.  PRACTICAL  DYNAMO-BUILDING  FOR  AMATEURS. 
HOW  TO  WIND  FOR  ANY  OUTPUT.  By  Frederick  Walker. 
Fully  illustrated. 

No.  99.  TRIPLE-EXPANSION  ENGINES  AND  ENGINE 
TRIALS.  By  Prof.  Osborne  Reynolds.  Edited,  with  notes,  etc.,  by 
F.  E.  Idell,  M.  E. 


SCIENCE  SERIES. 


No.  100.  HOW  TO  BECOME  AN  ENGINEER  ;  OR,  THE 
THEORETICAL  AND  PRACTICAL  TRAINING  NECESSARY  IN 
FITTING  FOR  THE  DUTIES  OF  THE  CIVIL  ENGINEER.  The 
Opinions  of  Eminent  Authorities,  and  the  Course  of  Study  in  the 
Technical  Schools.  By  Geo.  W.  Plympton,  Am.  Soc.  C.E. 

No.  101.  THE   SEXTANT  AND   OTHER   REFLECTING 

MATHEMATICAL  INSTRUMENTS.  With  Practical  Suggestions 
and  Wrinkles  on  their  Errors,  Adjustments,  and  Use.  With  thirty- 
three  illustrations.  By  F.  R.  Brainard,  U.S.N. 

No.  102.  THE  GALVANIC  CIRCUIT  INVESTIGATED 
MATHEMATICALLY.  By  Dr.  G.  S.  Ohm,  Berlin,  1827.  Translated 
by  William  Francis.  W.-li  Preface  and  Notes  by  the  Editor,  Thomas 
D.  Lockwood,  M.I.E.E. 

No.  103.  THE  MICROSCOPICAL  EXAMINATION  OF  POTA- 
BLE WATER.  With  Diagrams,  By  Geo.  W.  Rafter. 

No.  104.     VAN  NOSTRAND'S  TABLE-BOOK  FOR  CIVIL  AND 

MECHANICAL  ENGINEERS.    Compiled  by  Geo.  W.  Plympton,  C.E. 

No.  105.  DETERMINANTS,  AN  INTRODUCTION  TO  THE 

STUDY  OF.     With  examples.     By  Prof.  G.  A.  Miller. 

No.  106.  TRANSMISSION  BY  AIR-POWER.  Illustrated.  By 
Prof.  A.  B.  W.  Kennedy  and  W.  C.  Unwin. 

No.    107.     A  GRAPHICAL   METHOD   FOR  SWING-BRIDGES. 

A  Rational  and  Easy  Graphical  Analysis  of  the  Stresses  in  Ordinary 
Swing- Bridges.  With  an  Introduction  on  the  General  Theory  of  Graphi- 
cal Statics.  4  Plates.  By  Benjamin  F.  LaRue,  C.E. 

No.  108.  A  FRENCH  METHOD  FOR  OBTAINING  SLIDE- 
VALVE  DIAGRAMS.  8  Folcfing  Plates.  By  Lloyd  Bankson,  B.S., 
Assist.  Naval  Constructor,  U.S.N. 

No.  109.  THE  MEASUREMENT  OF  ELECTRIC  CURRENTS. 

ELECTRICAL  MEASURING  INSTRUMENTS.  By  Jas.  Swinburne.  METERS 
FOR  ELECTRICAL  ENERGY.  By  C.  H.  Wordingham.  Edited  by 
T.  Commerford  Martin.  Illustrated. 

No.  no.  TRANSITION  CURVES.  A  Field  Book  for  Engineers, 
containing  Rules  and  Tables  for  laying  out  Transition  Curves.  By 
Walter  G.  Fox. 

No.  in.  GAS-LIGHTING  AND  GAS-FITTING,  including  Specifica- 
tions and  Rules  for  Gas  Piping,  Notes  on  the  Advantages  of  Gas  for 
Cooking  and  Heating,  and  useful  Hints  to  Gas  Consumers.  Second 
edition,  rewritten  and  enlarged.  By  Wm.  Paul  Gerhard. 

No.  112.  A  PRIMER  ON  THE  CALCULUS.  By  E.  Sherman 
Gould,  C.E. 

No.  113.     PHYSICAL   PROBLEMS   AND    THEIR   SOLUTION. 

By  A.  Bourgougnon,  formerly  Assistant  at  Bellevue  Hospital. 

No.  114.  MANUAL  OF  THE  SLIDE  RULE.  By  F.  A.  Halsey  of 
the  American  Machinist.  Second  edition,  revised. 


SCIENCE    SERIES, 


No.  115.  TRAVERSE  TABLES,  showing  the  difference  of  Latitude 
and  Departure  for  distances  between  i  and  100  and  for  Angles  to 
Quarter  Degrees  between  I  degree  and  90  degrees.  (Reprinted  from 
Scribner's  Pocket  Table  Book.) 

No.  116.  WORM  AND  SPIRAL  GEARING.  Reprinted  from 
"American  Machinist."  By  F.  A.  Halsey. 


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by  Hutton 80 

132.  Dwelling  Houses,  Erection  of,  by  Brooks 1.00 

135.  Electro-metallurgy,  Watt 1.40 

136.  Arithmetic,  by  Haddon 60 

137.  Key  to  ditto 

138.  Telegraph,  Handbook  of ,  by  Bond 

139.  Steam  Engine,  Theory  of,  by  Baker 60 

140.  Farming— Soils,  Manures  and  Crops,  by  Burn.  .80 

141.  Ditto        Outlines — Farming  Economy,  by  Burn 1.20 

142.  Ditto        Cattle,  Sheep  and  Horses,  by  Burn 1.00 

143.  Experimental  Essays,  by  C.  Towlinson 

145.  Farming,  Dairy,  Pigs,  and  Poultry,  by  Burn 80 

146.  Ditto        Sewage,  Irrigation,  &c.,  by  Burn *. 1.00 

140  to  146.  The5vols.  in  1,  half-bound 4.80 

147.  The  Stepping  Stone  to  Arithmetic,  by  A.  Annan 

148.  Key  to  the  same 


D.  VAN  NOSTRAND  COMPANY'S 


No.  PRICE. 

149.  Sails  and  Sailmaking,  by  Kipping $1.00 

150.  Logic,   by  Emmens 60 

151.  Handy  Book  on  the  Law  of  Friendly,  Industrial  and  Provident  Build- 

ing and  Loan  Societies,  by  A.  White 

153.  Locke  on  the  Understanding,  by  Emmens 60 

154.  General  Hints  to  Emigrants 

155.  Engineer's  Guide  to  the  Navies 

156.  Quantities  and  Measurements,  by  Beaton 60 

157.  Emigrant's  Guide  to  Natal,  by  Dr.  Mann 

158.  Slide  Rule  and  How  to  Use  it,  by  Hoare 1.00 

162.  Brass  Founder's  Manual,  by  W.  Graham 80 

163.  Law  of  Patents  for  Invention,  by  F.  W.  Campin 

164.  Modern  Workshop  Practice,    by  J.  G.  Winton.     Fourth  Edition,  re-- 

vised and  enlarged 1.40 

165.  Iron  and  Heat,  by  Armour 1.00 

166.  Power  in  Motion,  by  Armour 80 

167.  Iron  Bridges,  Girders,  &c.,  by  Campin 

168.  Drawing  and  Measuring  Instruments,  by  Heather 63 

169.  Optical  Instruments,  by  Heather 60 

170.  Surveying  and  Astronomical  Instruments,  by  Heather 60 

168,  169,  170.  The  three  parts  as  above  in  1  vol 1.80 

*„*  The  above  form  an  enlargement  of  the  original  work,    "Mathematical 

Instruments  "  (No.  32). 
171    Engineering  Drawing,  by  John  Maxton 1.40 

172.  Mining  Tools,  by  William  Morgans*. 1.00 

172*.  Plates  to  ditto,  235  Engravings,  4to 1.80 

173-  Physical  Geology,  by  Portlock  and  Tate 80 

174.  Historical  Geology,  by  Ralph  Tate,  F.  G.  S 1.00 

173.  174.  Geology,  Portlock  and  Tate,  1  vol 1.80 

175.  Builder's  and  Contractor's  Price  Book 

176.  The  Metallurgy  of  Iron,  by  H.  Bauerman 2.00 

177.  Culture  of  Fruit  Trees,  by  Du  Breuil 1.40 

178.  Practical  Plane  Geometry,  by  J.  F.  Heather 80 

180.  Coal  and  Coal  Mining,  by  W.  W.  Smyth 1.40 

181.  Painting  (Fine  Art),  by  Gullick  and  Timbs 2.00 

182.  Carpentry  and  Joinery,  by  Tredgold  and  Tarn 1.40 

182*.  Atlas  of  35  plates  to  the  above 2.40 

183.  Animal  Physics,  by  Dr.  Lardner.     Parti 1.60 

184.  Ditto.     Part  II 1.20 

183,184.  Ditto.     In  1  Vol.     Cloth  boards 3.00 

185.  The  Complete  Measurer,  by  Richard  Horton 1.60 

186.  Grammar  of  Coloring,  by  Field,  Enlarged  by  Ellis  A.  Davidson,  with 

colored  plates 1.20 


SCIENTIFIC  PUBLICATIONS. 


No.  PBICE. 

187.  Hints  to  Young    Architects,    by  G.    Wightwick,  Enlarged  by  G.  H. 

Guillaume $1.40 

188.  House  Painting,  &c.,  by  Ellis  A.  Davidson 2.00 

189.  Practical  Bricklaying,  by  Adam  Hammond 60 

190.  Steam  and  the  Steam  Engine,  byD.  K.  Clark 1.40 

191.  Plumbing,   House    Drainage    and    Ventilation,   by  W.    P.  Buchan. 

Fifth  Edition,  Enlarged 1.40 

192.  Timber  Importers'  and  Builders'  Guide,  by  Grandy 80 

193.  Field  Fortification,  by  Major  W.  W.  Knollys 1.20 

194.  House  Manager,  by  an  Old  Housekeeper 1.40 

194,  112. 112*.  House  Book  (The).     Three  vols.  in  one,  half-bound 2.40 

196.  Compound  Interest  and  Annuities,  by  F.  Thoman 1.60 

197.  Roads  and  Streets,  by  Law  and  Clark 1.80 

198.  The  Sheep,  by  W.  C.  Spooner 1.40 

199.  The  Compendius  Calculator,  by  D.  O'Gorman,  revissd  by  C.  Norris....  1.00 

200.  Fuel,  by  C.  W.  Williams  and  D.  K.  Clark 1.40 

201.  Kitchen  Gardening  made  Easy,  by  Glenny 60 

202.  Locomotive  Engines,  by  Dempsey,  with  additions  by  D.  K.  Clark 1.20 

203.  Sanitary  Work,  by  Charles  Slagg 1.20 

204.  Mathematical  and  Nautical  Tables,   with  Treatise  on  Logarithms,  by 

Law  and  Young 1.60 

204*.  Logarithms,  Treatise  on,  with  Tables,  by  Law,  from  the  above 1.20 

204&55.  Practical  Navigation,  in  1  vol.,  half-bound 2.80 

205.  Letter  Painting  Made  Easy,  by  J.  G.  Badenoch 60 

206.  A  Book  on  Building,  by  Sir  Edmund  Beckett 1.80 

207.  Farm  Management,  by  K.  Scott  Burn 1.00 

208.  Landed  Estates  Management,  by  It.  Scott  Burn ,..  1.00 

207,  208.  Farm  and  Landed  Estates  Management,  by  R.  Scott  Burn,  in  1 

vol.,  half-bound 2.40 

209.  The  Tree  Planter  and  Plant  Propagator :  A  Practical  Manual,  by  Sam- 

uel Wood 80 

210.  The  Tree  Pruner,  by  Samuel  Wood 60 

209,  210.  The  Tree  Planter,  Propagator,  and  Pruner,  by  Samuel  Wood.    In 

1  vol.,  half-bound 1.40 

211.  The  Boilermaker's  Assistant,  by  Courtney 80 

212.  The  Construction  of  Gasworks,  by  S.  Hughes.     Seventh  Edition  by 

William  Richards 2.20 

213.  Pioneer  Engineering,  by  Edward  Dobson,  C.  E 1.80 

214.  Slate  and  Slate  Quarrying,  by  D.  C.  Davies 1.20 

215.  The  Goldsmith's  Handbook,  by  G.  E.  Gee 1.20 

216.  Materials  and  Construction,  by  F.  Campin 1.20 

217.  Sewing  Machinery,  by  J.  W.  Urquhart,  C.  E 80 

218.  Hay  and  Straw  Measurer,  by  John  Steele 80 


D.  VAN  NOSTRAND  COMPANY'S 


No.  PKICE. 

219.  Civil  Engineering,  by  Law  and  Burnell,  with  Eecent  Practice,  by  D. 

K.  Clarke,  M.  I.  C.  E $2.60 

221.  Measures,  Weights,  and  Moneys  of  All  Nations,  by  W.  S.  B.  Woolhouse. 

New  Edition 1.00 

222.  Suburban  Farming,  by  Prof .  Donaldson 

223.  Mechanical  Engineering,  by  F.  Camp  in,  C.  E 1.00 

224.  Coach  Building,  by  Jas.  W.  Burgess 1.00 

225.  The  Silversmith's  Handbook,  by  G.  E.  Gee 1.20 

215,  225.  The  Goldsmith's  and  Silversmith's  Complete  Handbook,  by  Gee. 

half-bound 2.80 

226.  The  Joints  used  by  Builders,  by  J.  W.   Christy 1.20 

227.  Mathematics  as  applied  to  the  Constructive  Arts,  by  F.  Campin,  C.  E.  1.20 

228.  The  Construction  of  Hoofs,  by  E.  W.  Tarn 60 

229.  Elementary  Decoration,  by  J.  W.  Facey 80 

230.  Hand  Railing  by  Geo.  Ceilings 1.00 

231.  Grafting  and  Buding,  by  C.  Baltet 1.00 

232.  Cottage  Gardening,  by  E.  Hobday 60 

233.  Garden  Receipts.     Edited  byC.  W.  Quin 60 

234.  Market  and  Kitchen  Gardening,  by  C.  W.  Shaw 1.20 

235.  Practical  Organ-Building,  by  Dickson 1.00 

236.  Details  of  Machinery,  byF.  Campin,  C.  E 1.20 

237.  The  Smithy  and  Forge,  by  Crane.     2d  Edition 1.00 

238.  Sheet  Metal  Workers'  Guide,  by  Crane 60 

239.  Draining  and  Embanking,  by  Prof .  Scott 60 

240.  Irrigation  and  Water  Supply,  by  Prof.  Scott 60 

241.  Farm  Roads,  Fences  and  Gates,  by  Prof .  Scott 60 

242.  Farm  Buildings,  by  Prof.  Scott 80 

243.  Barn  Implements  and  Machines,  by  Prof.  Scctt 80 

244.  Field  Implements  and  Machines,  by  Pros.  Scott 80 

245.  Agricultural  Surveying,  by  Prof .  Scott 60 

239  to  245.  The  7  vols.  in  1,  halt-bound 4.80 

246.  Dictionary  of  Painters,  by  P.  Datyl 1.00 

247.  Building  Estates,  by  Fowler  Maitland 80 

248.  Portland  Cement  for  Users,  by  Faija 80 

249.  The  Hail-Marking  of  Jewelry,  by  Gee 1.20 

250.  Meat  Production,  by  John  Ewart l.OC 

251.  Steam  and  Machinery  Management,  by  M.  Powis  Bale,  C.  E 1.00 

252.  Brickwork,  a  Practical  Treatise,  byF.  Walker.     2nd  Edition,  revised..     .60 
23,  189  &  252.  The  Practical  Brick  and  Tile  Book,  in  1  volume,  half -bound. 

253.  The  Timber  Merchant's  Freight  Book,  by  W.  Richardson  and  M.  P.  Bale, 

254.  The  Boilermaker's  Ready  Reckoner,  by  J.  Courtney,  revised  by  D. 

K.  Clark 1.60 

254  and  211  in  one  volume,  half  bound. 2.80 


SCIENTIFIC  PUBLICATIONS. 


No.  PEICE. 

256.  Stationary  Engine  Driving,  by  Michael  Reynolds $1.40 

257.  Practical  House  Decoration,  by  Facey 1.00 

229,  257.  House  Decoration,  by  Facey,  in  1  volume,  half -bound 2.00 

258.  Circular  Work  in  Carpentry,  by  Collings 1.00 

259.  Gas-Fitting,  by  John  Black 1.00 

260.  Iron  Bridges  of  Moderate  Span,  by  Hamilton  W.  Pendred 80 

261.  Shoring,  byGeo.  H.  Blagrove 60 

262.  Boot  and  Shoemaking,  by  J.  B.  Leno .80 

263.  Mechanical  Dentistry,  by  C.  Hunter 1.20 

264.  Mining  and   Quarrying,  by  J.  H.  Collins 60 

265.  Practical  Brick  Cutting  and  Setting,  by  Adam  Hammond. 60 

23,  189,  265  in  one  volume,  half  bound 2.40 

267.  The  Science  of  Building,  by  E.  W.  Tarn 1.40 

268.  The  Drainage  of  Lands,  Towns  and  Buildings,  by  G.  D.  Dempsey. 

Revised,  with  additions,  by  D.  K.  Clark.     2d  ed 1.80 

269.  Light;  an  Introduction  to  the  Science  of  Optics,  by  E.  W.  Tarn 60 

270.  Wood  Engraving,  by  W.  N.  Brown 60 

271,,     Ventilation,  by  W.  P.  Buchan 1.40 

272.  Roof  Carpentry,  by  George  Collings 80 

273.  The  Practical  Plasterer,  by  W.  Kemp 8C 

274.  Elementary  Marine  Engineering,  by  J.  S.  Brewer 60 

275.  Laundry  Management 80 

276.  Cement,  Pastes,  Glues  and  Gums,  by  H.  C.  Standage 80 

277.  Fuels  ;  Their  Analysis  and  Valuation,  by  H.  J.  Phillips 80 

278.  Model  Locomotive  Engineer,  Fireman,  &c.,  by  M.  Reynolds 1.40 

279.  Constructional  Iron  and  Steel  Work,  by  F.  Campin 1. 40 

280.  Iron  and  Steel  Bridges  and  Viaducts,  by  F.  Campin 1.40 

281.  French  Polishing  and  Enamelling,  by  R.  Bitmead 60 

282.  Electric  Lighting,  by  A.  A.  C.  Swinton 60 


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This  book  is  due  on  the  last  date  stamped  below,  or 
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